Merge pull request #56 from cashapp/fix-sign-cast

fix: cast to crypto.Signer instead of ecdsa.PrivateKey

Author: yoavamit

.gitignore

@@ -3,3 +3,4 @@ build
 .DS_Store
 result
 *~
+/cover.out

pkg/pivit/pivit.go

@@ -2,7 +2,6 @@ package pivit
 
 import (
 	"crypto"
-	"crypto/ecdsa"
 	"crypto/x509"
 	"fmt"
 	"io"
@@ -93,7 +92,7 @@ func (y signer) Sign(rand io.Reader, digest []byte, opts crypto.SignerOpts) ([]b
 	}
 
 	switch priv := private.(type) {
-	case *ecdsa.PrivateKey:
+	case crypto.Signer:
 		return priv.Sign(rand, digest, opts)
 	default:
 		return nil, fmt.Errorf("invalid key type")