Combine multiple error strings

I am new to golang, my application needs to return multiple errors in a loop, later requires to be combined and returned as a single error string. I am not able to use the string functions to combine the error messages. What methods can be use to combine these errors into a single error before returning ?

package main

import (
   "fmt"
   "strings"
)

func Servreturn() (err error) {

   err1 = fmt.Errorf("Something else occured")
   err2 = fmt.Errorf("Something else occured again")

   // concatenate both the error

   return err3

}