init関数のふしぎ #golang ref: https://qiita.com/tenntenn/items/7c70e3451ac783999b4f

file0.go

package main

import (
    "fmt"
)

func init() {
    fmt.Println("hello, init")
}

func main() {
    fmt.Println("Hello, main")
}

file0.txt

package main

import (
    "fmt"
)

func init() {
    fmt.Println("hello, init")
}

func main() {
    fmt.Println("Hello, main")
}

file1.go

package main

import (
    "fmt"
)

var msg = message()

func message() string {
    return "Hello"
}

func init() {
    fmt.Print(msg)
}

func main() {
    fmt.Println(", playground")
}

file1.txt

package main

import (
    "fmt"
)

var msg = message()

func message() string {
    return "Hello"
}

func init() {
    fmt.Print(msg)
}

func main() {
    fmt.Println(", playground")
}

file2.go

package main

import (
    "fmt"
)

func init() {
    fmt.Print("hello")
}

func init() {
    fmt.Println(", init")
}

func main() {
}

file2.txt

package main

import (
    "fmt"
)

func init() {
    fmt.Print("hello")
}

func init() {
    fmt.Println(", init")
}

func main() {
}

file3.go

package main

import (
    "fmt"
    "runtime"
)

func init() {
    var pcs [1]uintptr
    runtime.Callers(1, pcs[:])
    fn := runtime.FuncForPC(pcs[0])
    fmt.Println(fn.Name())
}

func init() {
    var pcs [1]uintptr
    runtime.Callers(1, pcs[:])
    fn := runtime.FuncForPC(pcs[0])
    fmt.Println(fn.Name())
}

func main() {
    var pcs [1]uintptr
    runtime.Callers(1, pcs[:])
    fn := runtime.FuncForPC(pcs[0])
    fmt.Println(fn.Name())
}

file3.txt

package main

import (
    "fmt"
    "runtime"
)

func init() {
    var pcs [1]uintptr
    runtime.Callers(1, pcs[:])
    fn := runtime.FuncForPC(pcs[0])
    fmt.Println(fn.Name())
}

func init() {
    var pcs [1]uintptr
    runtime.Callers(1, pcs[:])
    fn := runtime.FuncForPC(pcs[0])
    fmt.Println(fn.Name())
}

func main() {
    var pcs [1]uintptr
    runtime.Callers(1, pcs[:])
    fn := runtime.FuncForPC(pcs[0])
    fmt.Println(fn.Name())
}

file4.txt

main.init.1
main.init.2
main.main

file5.go

package main

import "fmt"

func init() {
    fmt.Println("hoge")
}

func main() {
    init()
}

file5.txt

package main

import "fmt"

func init() {
    fmt.Println("hoge")
}

func main() {
    init()
}

file6.txt

tmp/sandbox671239315/main.go:10: undefined: init