go - "undefined: hmac.Equal" error while hmac.New in the line before this works fine -

i developing web server in go,
@ top have

import ("net/http"     "log"     "fmt"     "encoding/json"     "encoding/hex"     "time"     "math/rand"     "crypto/sha256"     "crypto/hmac"     "strconv"     "strings"     "github.com/crowdmob/goamz/aws"     "github.com/crowdmob/goamz/dynamodb" ) 

later have

func singsomething(someid string) string { mac := hmac.new(sha256.new, key)     mac.write([]byte(id))     b := mac.sum(nil) return hex.encodetostring(b) }  func validatesignature(id, signature string) bool { mac := hmac.new(sha256.new, key)     mac.write([]byte(id))     expectedmac := mac.sum(nil)     signaturemac, err := hex.decodestring(signature)     if err != nil {     fmt.println("problem in decoding huh!")     return false     } return hmac.equal(expectedmac,signaturemac) 

}

i error when issue go run csserver
/csserver.go:54: undefined: hmac.equal

why? going on? how come hmac.new fine hmac.equals not?

please post minimal, complete programs when asking. without that, thing can provide example compiles w/o trouble, ie. undefined hmac.equal doesn't demonstrate. there must problem elsewhere in code didn't show.

package main  import (         "crypto/hmac"         "crypto/sha256"         "encoding/hex"         "fmt" )  func singsomething(someid string) string {         mac := hmac.new(sha256.new, []byte{})         mac.write([]byte(someid))         b := mac.sum(nil)         return hex.encodetostring(b) }  func validatesignature(id, signature string) bool {         mac := hmac.new(sha256.new, []byte{})         mac.write([]byte(id))         expectedmac := mac.sum(nil)         signaturemac, err := hex.decodestring(signature)         if err != nil {                 fmt.println("problem in decoding huh!")                 return false         }         return hmac.equal(expectedmac, signaturemac) }  func main() {} 

playground