gistfile1.go

package main

import (
  "fmt"
  "time"
)

type MyError struct {
  When time.Time
  Type, Message string
}

func (e *MyError) Error() string {
  return fmt.Sprintf("Error[%s]: %s <%v>",
    e.Type, e.Message, e.When)
}

func run() (str string, err error) {
  time := time.Now()
  str = ""
  err = nil
  
  if time.Minute() < 30 {
    err = &MyError{time, "TimeError", "You're under 30 minutes!"} 
  } else {
    str = "Past 30 minutes!"
  }
  return 
}

func main() {
  str, err := run()
  if err != nil {
    fmt.Println(err)
  } else {
    fmt.Println(str)
  }
}