get function info including comment / doc section

funcInfo.go

package main

import (
	"errors"
	"fmt"
	"go/ast"
	"go/doc"
	"go/parser"
	"go/token"
	"path/filepath"
	"reflect"
	"runtime"
	"strings"
)

// Info minimal info struct for function
type Info struct {
	FilePath     string
	FunctionName string
	Comment      string
	FunctionLine int
}

// function main
// this is the first line of comment
// this is the second line of comment
func main() {
	c, err := GetFunctionInfo(main)
	if err != nil {
		fmt.Println(err)
		return
	}

	fmt.Println("FilePath:", c.FilePath)
	fmt.Println("FunctionName:", c.FunctionName)
	fmt.Println("FunctionLine:", c.FunctionLine)
	fmt.Println("Comment:", c.Comment)
}

func GetFunctionInfo(f interface{}) (*Info, error) {
	ffpc := runtime.FuncForPC(reflect.ValueOf(f).Pointer())
	if ffpc == nil {
		return nil, errors.New("error. function program counter is nil")
	}

	filePath, functionLine := ffpc.FileLine(0)

	fset := token.NewFileSet()
	parsedAst, err := parser.ParseFile(fset, filePath, nil, parser.ParseComments)
	if err != nil {
		return nil, err
	}

	tokens := strings.Split(ffpc.Name(), ".")
	if len(tokens) != 2 {
		return nil, errors.New("error. func name split failed")
	}

	funcName := tokens[1]

	importPath, err := filepath.Abs("/")
	if err != nil {
		return nil, err
	}

	pkg := &ast.Package{
		Files: map[string]*ast.File{filePath: parsedAst},
	}

	myDoc := doc.New(pkg, importPath, doc.AllDecls)
	for _, theFunc := range myDoc.Funcs {
		if theFunc.Name == funcName {
			return &Info{
				FilePath:     filePath,
				FunctionName: funcName,
				Comment:      theFunc.Doc,
				FunctionLine: functionLine,
			}, nil
		}
	}
	return nil, nil
}