How to get name of current package in go?

Here a part of my logger package. It retrieves information about the caller of the logging function to show it later in the output.

func retrieveCallInfo() *callInfo {
    pc, file, line, _ := runtime.Caller(2)
    _, fileName := path.Split(file)
    parts := strings.Split(runtime.FuncForPC(pc).Name(), ".")
    pl := len(parts)
    packageName := ""
    funcName := parts[pl-1]

    if parts[pl-2][0] == '(' {
        funcName = parts[pl-2] + "." + funcName
        packageName = strings.Join(parts[0:pl-2], ".")
    } else {
        packageName = strings.Join(parts[0:pl-1], ".")
    }

    return &callInfo{
        packageName: packageName,
        fileName:    fileName,
        funcName:    funcName,
        line:        line,
    }
}

As you can see it returns the package name too.

To reliably get the package name, you can use the go compiler's parser to parse only the package clause.

import (
    "fmt"
    "go/ast"
    "go/parser"
    "go/token"
)

func packageName(file string) (string, error) {
    fset := token.NewFileSet()

    // parse the go soure file, but only the package clause
    astFile, err := parser.ParseFile(fset, l.path, nil, parser.PackageClauseOnly)
    if err != nil {
        return "", err
    }

    if astFile.Name == nil {
        return "", fmt.Errorf("no package name found")
    }

    return astFile.Name.Name, nil
}

There is no runtime or reflect method or function that provides the functionality that you are looking for.

The closest thing I could find is:

package main

import (
    "azul3d.org/lmath.v1"
    "fmt"
    "reflect"
)

type Empty struct{}

func main() {
    fmt.Println(reflect.TypeOf(Empty{}).PkgPath())
    fmt.Println(reflect.TypeOf(lmath.Vec3{0, 0, 0}).PkgPath())
}

This would output:

main
azul3d.org/lmath.v1

You could also read the first line of the file and remove the "package" substring. (Not sure if it's the best idea)

package main

import (
    "bufio"
    "bytes"
    "fmt"
    "os"
)

func main() {
    file, err := os.Open("so.go")
    if err != nil {
        panic(err)
    }
    r := bufio.NewReader(file)
    line, _, err := r.ReadLine()
    if err != nil {
        panic(err)
    }
    packageName := bytes.TrimPrefix(line, []byte("package "))
    fmt.Println(string(packageName))
}