Collect calls to http package parsing Go source files

parse.go

package main

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

var (
	dirFlag string
)

func main() {
	flag.StringVar(&dirFlag, "dir", "./", "Dir where to parse go files")
	flag.Parse()

	fset := token.NewFileSet()
	packages, err := parser.ParseDir(fset, dirFlag, nil, 0)
	if err != nil {
		fmt.Println(err)
		return
	}

	for _, pkg := range packages {
		for _, f := range pkg.Files {
			visitor := &callExprVisitor{f}
			ast.Walk(visitor, f)
		}
	}
}

type callExprVisitor struct {
	f *ast.File
}

func (v *callExprVisitor) Visit(n ast.Node) ast.Visitor {
	switch node := n.(type) {
	case *ast.File:
		return v
	case *ast.CallExpr:
		switch fn := node.Fun.(type) {
		case *ast.SelectorExpr:
			switch expr := fn.X.(type) {
			case *ast.Ident:
				if expr.Name == "http" {
					fmt.Printf("(%s) calling pkg http with %v\n", v.f.Name, fn.Sel)
				}
			}
		}
	}
	return v
}