Add gops agent

vendor/github.com/google/gops/internal/internal.go

@@ -0,0 +1,52 @@
+package internal
+
+import (
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"os/user"
+	"path/filepath"
+	"runtime"
+	"strings"
+)
+
+func ConfigDir() (string, error) {
+	if runtime.GOOS == "windows" {
+		return filepath.Join(os.Getenv("APPDATA"), "gops"), nil
+	}
+	homeDir := guessUnixHomeDir()
+	if homeDir == "" {
+		return "", errors.New("unable to get current user home directory: os/user lookup failed; $HOME is empty")
+	}
+	return filepath.Join(homeDir, ".config", "gops"), nil
+}
+
+func guessUnixHomeDir() string {
+	usr, err := user.Current()
+	if err == nil {
+		return usr.HomeDir
+	}
+	return os.Getenv("HOME")
+}
+
+func PIDFile(pid int) (string, error) {
+	gopsdir, err := ConfigDir()
+	if err != nil {
+		return "", err
+	}
+	return fmt.Sprintf("%s/%d", gopsdir, pid), nil
+}
+
+func GetPort(pid int) (string, error) {
+	portfile, err := PIDFile(pid)
+	if err != nil {
+		return "", err
+	}
+	b, err := ioutil.ReadFile(portfile)
+	if err != nil {
+		return "", err
+	}
+	port := strings.TrimSpace(string(b))
+	return port, nil
+}