Fix ignored err variables. (#498)

* Fix ignored err variables.

* Removed unneeded err return.

client_test.go

@@ -250,6 +250,9 @@ func TestClientConn(t *testing.T) {
 		t.Errorf("failed to exchange: %v", err)
 	}
 	r, err := cn.ReadMsg()
+	if err != nil {
+		t.Errorf("failed to get a valid answer: %v", err)
+	}
 	if r == nil || r.Rcode != RcodeSuccess {
 		t.Errorf("failed to get an valid answer\n%v", r)
 	}
@@ -263,6 +266,9 @@ func TestClientConn(t *testing.T) {
 	if buf == nil {
 		t.Errorf("failed to get an valid answer\n%v", r)
 	}
+	if err != nil {
+		t.Errorf("failed to get a valid answer: %v", err)
+	}
 	if int(h.Bits&0xF) != RcodeSuccess {
 		t.Errorf("failed to get an valid answer in ReadMsgHeader\n%v", r)
 	}

dns_test.go

@@ -154,6 +154,9 @@ func TestPack(t *testing.T) {
 	}
 	x.Answer = make([]RR, 1)
 	x.Answer[0], err = NewRR(rr[0])
+	if err != nil {
+		t.Fatal(err)
+	}
 	if _, err := x.Pack(); err == nil {
 		t.Error("packing should fail")
 	}

msg_helpers.go

@@ -96,7 +96,7 @@ func unpackHeader(msg []byte, off int) (rr RR_Header, off1 int, truncmsg []byte,
 		return hdr, len(msg), msg, err
 	}
 	msg, err = truncateMsgFromRdlength(msg, off, hdr.Rdlength)
-	return hdr, off, msg, nil
+	return hdr, off, msg, err
 }
 
 // pack packs an RR header, returning the offset to the end of the header.