关于go：init（）函数何时运行？


When is the init() function run?

我试图找到一个关于init()函数在go中的作用的精确解释。我读到了有效的go所说的，但我不确定我是否完全理解它所说的。我不确定的确切句子如下：

And finally means finally: init is called after all the variable declarations in the package have evaluated their initializers, and those are evaluated only after all the imported packages have been initialized.

号

all the variable declarations in the package have evaluated their initializers是什么意思？这是否意味着如果在包及其文件中声明"global"变量，in it()将不会运行，直到对所有变量进行计算，然后在运行/main_file_name时运行所有init函数，然后运行main()？

我还阅读了Mark Summerfield的Go Book，内容如下：

If a package has one or more init() functions they are automatically executed before the main package's main() function is called.

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在我的理解中，init()只在您运行时才相关，打算运行main()，对吗？或者是主包装。任何人都能更准确地理解我，请随时纠正我。

是的，假设你有：

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var WhatIsThe = AnswerToLife()

func AnswerToLife() int {
    return 42
}

func init() {
    WhatIsThe = 0
}

func main() {
    if WhatIsThe == 0 {
        fmt.Println("It's all a lie.")
    }
}

AnswerToLife()保证在init()调用前运行，init()保证在main()调用前运行。

请记住，无论是否有MAIN，总是调用init()，因此，如果导入一个具有init功能的包，它将被执行。

//编辑

另外，请记住，每个包可以有多个init()函数，它们将按照它们在代码中显示的顺序执行(当然，在初始化所有变量之后)。

//编辑2X

许多内部go包使用init()初始化表，例如https://github.com/golang/go/blob/883bc6/src/compress/bzip2/bzip2.go l480

//编辑3X

@benc在同一个包执行顺序中有多个init:

It seems that init() functions are executed in lexical file name order. The Go spec says"build systems are encouraged to present multiple files belonging to the same package in lexical file name order to a compiler". It seems that go build works this way.

相关讨论

看这张照片。：)

import --> const --> var --> init()

></P></p> <li><P>如果包导入其他包，则首先初始化导入的包。</P></li> <li><P>当前包的常量已初始化。</P></li> <li><P>然后初始化当前包的变量。</P></li> <li><P>最后调用当前包的<wyn>init()</wyn>函数。</P></li> <blockquote> <p> A package can have multiple init functions (either in a single file or distributed across multiple files) and they are called in the order in which they are presented to the compiler. </p> </blockquote> <p><P>< BR></P></p> <blockquote> <p> A package will be initialised only once even if it is imported from multiple packages. </p> </blockquote> <div class=

相关讨论

要添加的内容(我本来可以添加为评论，但写这篇文章的时间我还没有足够的声誉)

在同一个包中有多个init，我还没有找到任何有保证的方法来知道它们的运行顺序。例如，我有：

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package config
    - config.go
    - router.go

config.go和router.go都包含init()函数，但是在运行router.go函数时，它首先运行(这导致我的应用程序恐慌)。

如果您处于多个文件的情况下，每个文件都有自己的init()函数，那么请注意，您不一定会先得到一个文件。在他的例子中，最好使用一对一的变量赋值。最好的部分是：这个变量声明将发生在包中所有init()函数之前。

例如

配置：

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var ConfigSuccess = configureApplication()

func init() {
    doSomething()
}

func configureApplication() bool {
    l4g.Info("Configuring application...")
    if valid := loadCommandLineFlags(); !valid {
        l4g.Critical("Failed to load Command Line Flags")
        return false
    }
    return true
}

路由器：

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func init() {
    var (
        rwd string
        tmp string
        ok  bool
    )
    if metapath, ok := Config["fs"]["metapath"].(string); ok {
        var err error
        Conn, err = services.NewConnection(metapath +"/metadata.db")
        if err != nil {
            panic(err)
        }
    }
}

无论router.go或config.go中是否存在var ConfigSuccess = configureApplication()，它都将在init()运行之前运行。

相关讨论

下面是另一个示例-https://github.com/alok87/gobyexample/blob/master/init/init.go

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package main

import (
   "fmt"
)

func callOut() int {
    fmt.Println("Outside is beinge executed")
    return 1
}

var test = callOut()

func init() {
    fmt.Println("Init3 is being executed")
}

func init() {
    fmt.Println("Init is being executed")
}

func init() {
    fmt.Println("Init2 is being executed")
}

func main() {
    fmt.Println("Do your thing !")
}

上述程序的输出

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$ go run init/init.go
Outside is being executed
Init3 is being executed
Init is being executed
Init2 is being executed
Do your thing !

例如，为其他用户设计的框架或库，这些用户最终会在代码中包含一个main function，以便执行其应用程序。如果用户直接导入库项目的子包，那么该子包的init首先将被调用(一次)。库等的根包也是如此…

有时，您可能希望在不存在main func的情况下直接或不执行代码块。

如果您作为虚拟库的开发人员，导入具有init函数的库的子包，则会首先调用它，并且一旦调用它，您就没有main func函数，但需要确保在调用其他函数之前初始化某些变量或表。

一件值得记住而不必担心的事情是：init总是每个应用程序执行一次。

执行发生：

  • 在"调用者"包的init功能之前，
  • 在(可选)main func之前，
  • 但在包级变量var = [...] or cost = [...]之后，

    • 当您导入一个包时，它将按顺序运行它的所有init函数。

    我将给出一个非常好的init函数示例。它将向名为mime的标准go库中添加mime类型，包级函数将直接使用mime标准包来获取在其init函数中已经初始化的自定义mime类型：

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    package mime

    import (
       "mime"
       "path/filepath"
    )

    var types = map[string]string{
       ".3dm":      "x-world/x-3dmf",
       ".3dmf":     "x-world/x-3dmf",
       ".7z":       "application/x-7z-compressed",
       ".a":        "application/octet-stream",
       ".aab":      "application/x-authorware-bin",
       ".aam":      "application/x-authorware-map",
       ".aas":      "application/x-authorware-seg",
       ".abc":      "text/vndabc",
       ".ace":      "application/x-ace-compressed",
       ".acgi":     "text/html",
       ".afl":      "video/animaflex",
       ".ai":       "application/postscript",
       ".aif":      "audio/aiff",
       ".aifc":     "audio/aiff",
       ".aiff":     "audio/aiff",
       ".aim":      "application/x-aim",
       ".aip":      "text/x-audiosoft-intra",
       ".alz":      "application/x-alz-compressed",
       ".ani":      "application/x-navi-animation",
       ".aos":      "application/x-nokia-9000-communicator-add-on-software",
       ".aps":      "application/mime",
       ".apk":      "application/vnd.android.package-archive",
       ".arc":      "application/x-arc-compressed",
       ".arj":      "application/arj",
       ".art":      "image/x-jg",
       ".asf":      "video/x-ms-asf",
       ".asm":      "text/x-asm",
       ".asp":      "text/asp",
       ".asx":      "application/x-mplayer2",
       ".au":       "audio/basic",
       ".avi":      "video/x-msvideo",
       ".avs":      "video/avs-video",
       ".bcpio":    "application/x-bcpio",
       ".bin":      "application/mac-binary",
       ".bmp":      "image/bmp",
       ".boo":      "application/book",
       ".book":     "application/book",
       ".boz":      "application/x-bzip2",
       ".bsh":      "application/x-bsh",
       ".bz2":      "application/x-bzip2",
       ".bz":       "application/x-bzip",
       ".c++":      "text/plain",
       ".c":        "text/x-c",
       ".cab":      "application/vnd.ms-cab-compressed",
       ".cat":      "application/vndms-pkiseccat",
       ".cc":       "text/x-c",
       ".ccad":     "application/clariscad",
       ".cco":      "application/x-cocoa",
       ".cdf":      "application/cdf",
       ".cer":      "application/pkix-cert",
       ".cha":      "application/x-chat",
       ".chat":     "application/x-chat",
       ".chrt":     "application/vnd.kde.kchart",
       ".class":    "application/java",
       ".com":      "text/plain",
       ".conf":     "text/plain",
       ".cpio":     "application/x-cpio",
       ".cpp":      "text/x-c",
       ".cpt":      "application/mac-compactpro",
       ".crl":      "application/pkcs-crl",
       ".crt":      "application/pkix-cert",
       ".crx":      "application/x-chrome-extension",
       ".csh":      "text/x-scriptcsh",
       ".css":      "text/css",
       ".csv":      "text/csv",
       ".cxx":      "text/plain",
       ".dar":      "application/x-dar",
       ".dcr":      "application/x-director",
       ".deb":      "application/x-debian-package",
       ".deepv":    "application/x-deepv",
       ".def":      "text/plain",
       ".der":      "application/x-x509-ca-cert",
       ".dif":      "video/x-dv",
       ".dir":      "application/x-director",
       ".divx":     "video/divx",
       ".dl":       "video/dl",
       ".dmg":      "application/x-apple-diskimage",
       ".doc":      "application/msword",
       ".dot":      "application/msword",
       ".dp":       "application/commonground",
       ".drw":      "application/drafting",
       ".dump":     "application/octet-stream",
       ".dv":       "video/x-dv",
       ".dvi":      "application/x-dvi",
       ".dwf":      "drawing/x-dwf=(old)",
       ".dwg":      "application/acad",
       ".dxf":      "application/dxf",
       ".dxr":      "application/x-director",
       ".el":       "text/x-scriptelisp",
       ".elc":      "application/x-bytecodeelisp=(compiled=elisp)",
       ".eml":      "message/rfc822",
       ".env":      "application/x-envoy",
       ".eps":      "application/postscript",
       ".es":       "application/x-esrehber",
       ".etx":      "text/x-setext",
       ".evy":      "application/envoy",
       ".exe":      "application/octet-stream",
       ".f77":      "text/x-fortran",
       ".f90":      "text/x-fortran",
       ".f":        "text/x-fortran",
       ".fdf":      "application/vndfdf",
       ".fif":      "application/fractals",
       ".fli":      "video/fli",
       ".flo":      "image/florian",
       ".flv":      "video/x-flv",
       ".flx":      "text/vndfmiflexstor",
       ".fmf":      "video/x-atomic3d-feature",
       ".for":      "text/x-fortran",
       ".fpx":      "image/vndfpx",
       ".frl":      "application/freeloader",
       ".funk":     "audio/make",
       ".g3":       "image/g3fax",
       ".g":        "text/plain",
       ".gif":      "image/gif",
       ".gl":       "video/gl",
       ".gsd":      "audio/x-gsm",
       ".gsm":      "audio/x-gsm",
       ".gsp":      "application/x-gsp",
       ".gss":      "application/x-gss",
       ".gtar":     "application/x-gtar",
       ".gz":       "application/x-compressed",
       ".gzip":     "application/x-gzip",
       ".h":        "text/x-h",
       ".hdf":      "application/x-hdf",
       ".help":     "application/x-helpfile",
       ".hgl":      "application/vndhp-hpgl",
       ".hh":       "text/x-h",
       ".hlb":      "text/x-script",
       ".hlp":      "application/hlp",
       ".hpg":      "application/vndhp-hpgl",
       ".hpgl":     "application/vndhp-hpgl",
       ".hqx":      "application/binhex",
       ".hta":      "application/hta",
       ".htc":      "text/x-component",
       ".htm":      "text/html",
       ".html":     "text/html",
       ".htmls":    "text/html",
       ".htt":      "text/webviewhtml",
       ".htx":      "text/html",
       ".ice":      "x-conference/x-cooltalk",
       ".ico":      "image/x-icon",
       ".ics":      "text/calendar",
       ".icz":      "text/calendar",
       ".idc":      "text/plain",
       ".ief":      "image/ief",
       ".iefs":     "image/ief",
       ".iges":     "application/iges",
       ".igs":      "application/iges",
       ".ima":      "application/x-ima",
       ".imap":     "application/x-httpd-imap",
       ".inf":      "application/inf",
       ".ins":      "application/x-internett-signup",
       ".ip":       "application/x-ip2",
       ".isu":      "video/x-isvideo",
       ".it":       "audio/it",
       ".iv":       "application/x-inventor",
       ".ivr":      "i-world/i-vrml",
       ".ivy":      "application/x-livescreen",
       ".jam":      "audio/x-jam",
       ".jav":      "text/x-java-source",
       ".java":     "text/x-java-source",
       ".jcm":      "application/x-java-commerce",
       ".jfif-tbnl":"image/jpeg",
       ".jfif":     "image/jpeg",
       ".jnlp":     "application/x-java-jnlp-file",
       ".jpe":      "image/jpeg",
       ".jpeg":     "image/jpeg",
       ".jpg":      "image/jpeg",
       ".jps":      "image/x-jps",
       ".js":       "application/javascript",
       ".json":     "application/json",
       ".jut":      "image/jutvision",
       ".kar":      "audio/midi",
       ".karbon":   "application/vnd.kde.karbon",
       ".kfo":      "application/vnd.kde.kformula",
       ".flw":      "application/vnd.kde.kivio",
       ".kml":      "application/vnd.google-earth.kml+xml",
       ".kmz":      "application/vnd.google-earth.kmz",
       ".kon":      "application/vnd.kde.kontour",
       ".kpr":      "application/vnd.kde.kpresenter",
       ".kpt":      "application/vnd.kde.kpresenter",
       ".ksp":      "application/vnd.kde.kspread",
       ".kwd":      "application/vnd.kde.kword",
       ".kwt":      "application/vnd.kde.kword",
       ".ksh":      "text/x-scriptksh",
       ".la":       "audio/nspaudio",
       ".lam":      "audio/x-liveaudio",
       ".latex":    "application/x-latex",
       ".lha":      "application/lha",
       ".lhx":      "application/octet-stream",
       ".list":     "text/plain",
       ".lma":      "audio/nspaudio",
       ".log":      "text/plain",
       ".lsp":      "text/x-scriptlisp",
       ".lst":      "text/plain",
       ".lsx":      "text/x-la-asf",
       ".ltx":      "application/x-latex",
       ".lzh":      "application/octet-stream",
       ".lzx":      "application/lzx",
       ".m1v":      "video/mpeg",
       ".m2a":      "audio/mpeg",
       ".m2v":      "video/mpeg",
       ".m3u":      "audio/x-mpegurl",
       ".m":        "text/x-m",
       ".man":      "application/x-troff-man",
       ".manifest": "text/cache-manifest",
       ".map":      "application/x-navimap",
       ".mar":      "text/plain",
       ".mbd":      "application/mbedlet",
       ".mc$":      "application/x-magic-cap-package-10",
       ".mcd":      "application/mcad",
       ".mcf":      "text/mcf",
       ".mcp":      "application/netmc",
       ".me":       "application/x-troff-me",
       ".mht":      "message/rfc822",
       ".mhtml":    "message/rfc822",
       ".mid":      "application/x-midi",
       ".midi":     "application/x-midi",
       ".mif":      "application/x-frame",
       ".mime":     "message/rfc822",
       ".mjf":      "audio/x-vndaudioexplosionmjuicemediafile",
       ".mjpg":     "video/x-motion-jpeg",
       ".mm":       "application/base64",
       ".mme":      "application/base64",
       ".mod":      "audio/mod",
       ".moov":     "video/quicktime",
       ".mov":      "video/quicktime",
       ".movie":    "video/x-sgi-movie",
       ".mp2":      "audio/mpeg",
       ".mp3":      "audio/mpeg3",
       ".mp4":      "video/mp4",
       ".mpa":      "audio/mpeg",
       ".mpc":      "application/x-project",
       ".mpe":      "video/mpeg",
       ".mpeg":     "video/mpeg",
       ".mpg":      "video/mpeg",
       ".mpga":     "audio/mpeg",
       ".mpp":      "application/vndms-project",
       ".mpt":      "application/x-project",
       ".mpv":      "application/x-project",
       ".mpx":      "application/x-project",
       ".mrc":      "application/marc",
       ".ms":       "application/x-troff-ms",
       ".mv":       "video/x-sgi-movie",
       ".my":       "audio/make",
       ".mzz":      "application/x-vndaudioexplosionmzz",
       ".nap":      "image/naplps",
       ".naplps":   "image/naplps",
       ".nc":       "application/x-netcdf",
       ".ncm":      "application/vndnokiaconfiguration-message",
       ".nif":      "image/x-niff",
       ".niff":     "image/x-niff",
       ".nix":      "application/x-mix-transfer",
       ".nsc":      "application/x-conference",
       ".nvd":      "application/x-navidoc",
       ".o":        "application/octet-stream",
       ".oda":      "application/oda",
       ".odb":      "application/vnd.oasis.opendocument.database",
       ".odc":      "application/vnd.oasis.opendocument.chart",
       ".odf":      "application/vnd.oasis.opendocument.formula",
       ".odg":      "application/vnd.oasis.opendocument.graphics",
       ".odi":      "application/vnd.oasis.opendocument.image",
       ".odm":      "application/vnd.oasis.opendocument.text-master",
       ".odp":      "application/vnd.oasis.opendocument.presentation",
       ".ods":      "application/vnd.oasis.opendocument.spreadsheet",
       ".odt":      "application/vnd.oasis.opendocument.text",
       ".oga":      "audio/ogg",
       ".ogg":      "audio/ogg",
       ".ogv":      "video/ogg",
       ".omc":      "application/x-omc",
       ".omcd":     "application/x-omcdatamaker",
       ".omcr":     "application/x-omcregerator",
       ".otc":      "application/vnd.oasis.opendocument.chart-template",
       ".otf":      "application/vnd.oasis.opendocument.formula-template",
       ".otg":      "application/vnd.oasis.opendocument.graphics-template",
       ".oth":      "application/vnd.oasis.opendocument.text-web",
       ".oti":      "application/vnd.oasis.opendocument.image-template",
       ".otm":      "application/vnd.oasis.opendocument.text-master",
       ".otp":      "application/vnd.oasis.opendocument.presentation-template",
       ".ots":      "application/vnd.oasis.opendocument.spreadsheet-template",
       ".ott":      "application/vnd.oasis.opendocument.text-template",
       ".p10":      "application/pkcs10",
       ".p12":      "application/pkcs-12",
       ".p7a":      "application/x-pkcs7-signature",
       ".p7c":      "application/pkcs7-mime",
       ".p7m":      "application/pkcs7-mime",
       ".p7r":      "application/x-pkcs7-certreqresp",
       ".p7s":      "application/pkcs7-signature",
       ".p":        "text/x-pascal",
       ".part":     "application/pro_eng",
       ".pas":      "text/pascal",
       ".pbm":      "image/x-portable-bitmap",
       ".pcl":      "application/vndhp-pcl",
       ".pct":      "image/x-pict",
       ".pcx":      "image/x-pcx",
       ".pdb":      "chemical/x-pdb",
       ".pdf":      "application/pdf",
       ".pfunk":    "audio/make",
       ".pgm":      "image/x-portable-graymap",
       ".pic":      "image/pict",
       ".pict":     "image/pict",
       ".pkg":      "application/x-newton-compatible-pkg",
       ".pko":      "application/vndms-pkipko",
       ".pl":       "text/x-scriptperl",
       ".plx":      "application/x-pixclscript",
       ".pm4":      "application/x-pagemaker",
       ".pm5":      "application/x-pagemaker",
       ".pm":       "text/x-scriptperl-module",
       ".png":      "image/png",
       ".pnm":      "application/x-portable-anymap",
       ".pot":      "application/mspowerpoint",
       ".pov":      "model/x-pov",
       ".ppa":      "application/vndms-powerpoint",
       ".ppm":      "image/x-portable-pixmap",
       ".pps":      "application/mspowerpoint",
       ".ppt":      "application/mspowerpoint",
       ".ppz":      "application/mspowerpoint",
       ".pre":      "application/x-freelance",
       ".prt":      "application/pro_eng",
       ".ps":       "application/postscript",
       ".psd":      "application/octet-stream",
       ".pvu":      "paleovu/x-pv",
       ".pwz":      "application/vndms-powerpoint",
       ".py":       "text/x-scriptphyton",
       ".pyc":      "application/x-bytecodepython",
       ".qcp":      "audio/vndqcelp",
       ".qd3":      "x-world/x-3dmf",
       ".qd3d":     "x-world/x-3dmf",
       ".qif":      "image/x-quicktime",
       ".qt":       "video/quicktime",
       ".qtc":      "video/x-qtc",
       ".qti":      "image/x-quicktime",
       ".qtif":     "image/x-quicktime",
       ".ra":       "audio/x-pn-realaudio",
       ".ram":      "audio/x-pn-realaudio",
       ".rar":      "application/x-rar-compressed",
       ".ras":      "application/x-cmu-raster",
       ".rast":     "image/cmu-raster",
       ".rexx":     "text/x-scriptrexx",
       ".rf":       "image/vndrn-realflash",
       ".rgb":      "image/x-rgb",
       ".rm":       "application/vndrn-realmedia",
       ".rmi":      "audio/mid",
       ".rmm":      "audio/x-pn-realaudio",
       ".rmp":      "audio/x-pn-realaudio",
       ".rng":      "application/ringing-tones",
       ".rnx":      "application/vndrn-realplayer",
       ".roff":     "application/x-troff",
       ".rp":       "image/vndrn-realpix",
       ".rpm":      "audio/x-pn-realaudio-plugin",
       ".rt":       "text/vndrn-realtext",
       ".rtf":      "text/richtext",
       ".rtx":      "text/richtext",
       ".rv":       "video/vndrn-realvideo",
       ".s":        "text/x-asm",
       ".s3m":      "audio/s3m",
       ".s7z":      "application/x-7z-compressed",
       ".saveme":   "application/octet-stream",
       ".sbk":      "application/x-tbook",
       ".scm":      "text/x-scriptscheme",
       ".sdml":     "text/plain",
       ".sdp":      "application/sdp",
       ".sdr":      "application/sounder",
       ".sea":      "application/sea",
       ".set":      "application/set",
       ".sgm":      "text/x-sgml",
       ".sgml":     "text/x-sgml",
       ".sh":       "text/x-scriptsh",
       ".shar":     "application/x-bsh",
       ".shtml":    "text/x-server-parsed-html",
       ".sid":      "audio/x-psid",
       ".skd":      "application/x-koan",
       ".skm":      "application/x-koan",
       ".skp":      "application/x-koan",
       ".skt":      "application/x-koan",
       ".sit":      "application/x-stuffit",
       ".sitx":     "application/x-stuffitx",
       ".sl":       "application/x-seelogo",
       ".smi":      "application/smil",
       ".smil":     "application/smil",
       ".snd":      "audio/basic",
       ".sol":      "application/solids",
       ".spc":      "text/x-speech",
       ".spl":      "application/futuresplash",
       ".spr":      "application/x-sprite",
       ".sprite":   "application/x-sprite",
       ".spx":      "audio/ogg",
       ".src":      "application/x-wais-source",
       ".ssi":      "text/x-server-parsed-html",
       ".ssm":      "application/streamingmedia",
       ".sst":      "application/vndms-pkicertstore",
       ".step":     "application/step",
       ".stl":      "application/sla",
       ".stp":      "application/step",
       ".sv4cpio":  "application/x-sv4cpio",
       ".sv4crc":   "application/x-sv4crc",
       ".svf":      "image/vnddwg",
       ".svg":      "image/svg+xml",
       ".svr":      "application/x-world",
       ".swf":      "application/x-shockwave-flash",
       ".t":        "application/x-troff",
       ".talk":     "text/x-speech",
       ".tar":      "application/x-tar",
       ".tbk":      "application/toolbook",
       ".tcl":      "text/x-scripttcl",
       ".tcsh":     "text/x-scripttcsh",
       ".tex":      "application/x-tex",
       ".texi":     "application/x-texinfo",
       ".texinfo":  "application/x-texinfo",
       ".text":     "text/plain",
       ".tgz":      "application/gnutar",
       ".tif":      "image/tiff",
       ".tiff":     "image/tiff",
       ".tr":       "application/x-troff",
       ".tsi":      "audio/tsp-audio",
       ".tsp":      "application/dsptype",
       ".tsv":      "text/tab-separated-values",
       ".turbot":   "image/florian",
       ".txt":      "text/plain",
       ".uil":      "text/x-uil",
       ".uni":      "text/uri-list",
       ".unis":     "text/uri-list",
       ".unv":      "application/i-deas",
       ".uri":      "text/uri-list",
       ".uris":     "text/uri-list",
       ".ustar":    "application/x-ustar",
       ".uu":       "text/x-uuencode",
       ".uue":      "text/x-uuencode",
       ".vcd":      "application/x-cdlink",
       ".vcf":      "text/x-vcard",
       ".vcard":    "text/x-vcard",
       ".vcs":      "text/x-vcalendar",
       ".vda":      "application/vda",
       ".vdo":      "video/vdo",
       ".vew":      "application/groupwise",
       ".viv":      "video/vivo",
       ".vivo":     "video/vivo",
       ".vmd":      "application/vocaltec-media-desc",
       ".vmf":      "application/vocaltec-media-file",
       ".voc":      "audio/voc",
       ".vos":      "video/vosaic",
       ".vox":      "audio/voxware",
       ".vqe":      "audio/x-twinvq-plugin",
       ".vqf":      "audio/x-twinvq",
       ".vql":      "audio/x-twinvq-plugin",
       ".vrml":     "application/x-vrml",
       ".vrt":      "x-world/x-vrt",
       ".vsd":      "application/x-visio",
       ".vst":      "application/x-visio",
       ".vsw":      "application/x-visio",
       ".w60":      "application/wordperfect60",
       ".w61":      "application/wordperfect61",
       ".w6w":      "application/msword",
       ".wav":      "audio/wav",
       ".wb1":      "application/x-qpro",
       ".wbmp":     "image/vnd.wap.wbmp",
       ".web":      "application/vndxara",
       ".wiz":      "application/msword",
       ".wk1":      "application/x-123",
       ".wmf":      "windows/metafile",
       ".wml":      "text/vnd.wap.wml",
       ".wmlc":     "application/vnd.wap.wmlc",
       ".wmls":     "text/vnd.wap.wmlscript",
       ".wmlsc":    "application/vnd.wap.wmlscriptc",
       ".word":     "application/msword",
       ".wp5":      "application/wordperfect",
       ".wp6":      "application/wordperfect",
       ".wp":       "application/wordperfect",
       ".wpd":      "application/wordperfect",
       ".wq1":      "application/x-lotus",
       ".wri":      "application/mswrite",
       ".wrl":      "application/x-world",
       ".wrz":      "model/vrml",
       ".wsc":      "text/scriplet",
       ".wsrc":     "application/x-wais-source",
       ".wtk":      "application/x-wintalk",
       ".x-png":    "image/png",
       ".xbm":      "image/x-xbitmap",
       ".xdr":      "video/x-amt-demorun",
       ".xgz":      "xgl/drawing",
       ".xif":      "image/vndxiff",
       ".xl":       "application/excel",
       ".xla":      "application/excel",
       ".xlb":      "application/excel",
       ".xlc":      "application/excel",
       ".xld":      "application/excel",
       ".xlk":      "application/excel",
       ".xll":      "application/excel",
       ".xlm":      "application/excel",
       ".xls":      "application/excel",
       ".xlt":      "application/excel",
       ".xlv":      "application/excel",
       ".xlw":      "application/excel",
       ".xm":       "audio/xm",
       ".xml":      "text/xml",
       ".xmz":      "xgl/movie",
       ".xpix":     "application/x-vndls-xpix",
       ".xpm":      "image/x-xpixmap",
       ".xsr":      "video/x-amt-showrun",
       ".xwd":      "image/x-xwd",
       ".xyz":      "chemical/x-pdb",
       ".z":        "application/x-compress",
       ".zip":      "application/zip",
       ".zoo":      "application/octet-stream",
       ".zsh":      "text/x-scriptzsh",
       ".docx":     "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
       ".docm":     "application/vnd.ms-word.document.macroEnabled.12",
       ".dotx":     "application/vnd.openxmlformats-officedocument.wordprocessingml.template",
       ".dotm":     "application/vnd.ms-word.template.macroEnabled.12",
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       ".xlsm":     "application/vnd.ms-excel.sheet.macroEnabled.12",
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       ".xlsb":     "application/vnd.ms-excel.sheet.binary.macroEnabled.12",
       ".xlam":     "application/vnd.ms-excel.addin.macroEnabled.12",
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       ".ppsx":     "application/vnd.openxmlformats-officedocument.presentationml.slideshow",
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       ".potx":     "application/vnd.openxmlformats-officedocument.presentationml.template",
       ".potm":     "application/vnd.ms-powerpoint.template.macroEnabled.12",
       ".ppam":     "application/vnd.ms-powerpoint.addin.macroEnabled.12",
       ".sldx":     "application/vnd.openxmlformats-officedocument.presentationml.slide",
       ".sldm":     "application/vnd.ms-powerpoint.slide.macroEnabled.12",
       ".thmx":     "application/vnd.ms-officetheme",
       ".onetoc":   "application/onenote",
       ".onetoc2":  "application/onenote",
       ".onetmp":   "application/onenote",
       ".onepkg":   "application/onenote",
       ".xpi":      "application/x-xpinstall",
    }

    func init() {
        for ext, typ := range types {
            // skip errors
            mime.AddExtensionType(ext, typ)
        }
    }

    // typeByExtension returns the MIME type associated with the file extension ext.
    // The extension ext should begin with a leading dot, as in".html".
    // When ext has no associated type, typeByExtension returns"".
    //
    // Extensions are looked up first case-sensitively, then case-insensitively.
    //
    // The built-in table is small but on unix it is augmented by the local
    // system's mime.types file(s) if available under one or more of these
    // names:
    //
    //   /etc/mime.types
    //   /etc/apache2/mime.types
    //   /etc/apache/mime.types
    //
    // On Windows, MIME types are extracted from the registry.
    //
    // Text types have the charset parameter set to"utf-8" by default.
    func TypeByExtension(fullfilename string) string {
        ext := filepath.Ext(fullfilename)
        typ := mime.TypeByExtension(ext)

        // mime.TypeByExtension returns as text/plain; | charset=utf-8 the static .js (not always)
        if ext ==".js" && (typ =="text/plain" || typ =="text/plain; charset=utf-8") {

            if ext ==".js" {
                typ ="application/javascript"
            }
        }
        return typ
    }

    希望对您和其他用户有所帮助，如果您有更多问题，请不要犹豫，再次发帖！

    一个包中的mutil init函数执行顺序：

  • const和变量定义的文件init()函数execute

  • init函数按文件名asc执行顺序

    • init将在任何地方调用使用它的包(无论是空白导入还是导入)，但只有一次。

    这是一个包：

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    package demo

    import (
       "some/logs"
    )

    var count int

    func init() {
        logs.Debug(count)
    }

    // Do do
    func Do() {
        logs.Debug("dd")
    }

    任何包(主包或任何测试包)将其作为空白导入：

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    _"printfcoder.com/we/models/demo"

    或者使用函数导入：

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    "printfcoder.com/we/models/demo"

    func someFunc(){
       demo.Do()
    }

    init将只记录一次0。第一个使用它的包的init func将在包的init之前运行。所以：

    A调用B，B调用C，它们都有init func，C的init将在B之前运行，B在A之前运行。

    https://golang.org/ref/mem_tmp_4

    Program initialization runs in a single goroutine, but that goroutine may create other goroutines, which run concurrently.

    If a package p imports package q, the completion of q's init functions happens before the start of any of p's.

    The start of the function main.main happens after all init functions have finished.

    init func先运行，然后运行main。它用于在程序运行之前先设置一些内容，例如：

    访问模板，使用所有核心运行程序，正在检查goos和arch等…