8	func check(err error) {
     9		if err != nil {
    10			panic(err)
    11		}
    12	}
    13	
    14	func f() (err error) {
    15		err = e1()
    16		if err != nil {
    17			return err
    18		}
    19	
    20		// Oops!  Forgot to replace "_" with "err" after debugging.
    21		_ = e2()
    22		if err != nil {
    23			return err
    24		}
    25	
    26		return nil
    27	}
    28	
    29	func g() {
    30		var err error
    31	
    32		err = e1()
    33		check(err)
    34	
    35		// Oops!  Forgot to replace "_" with "err" after debugging.
    36		_ = e2()
    37		check(err)
    38	}