Fix lint

mtglib/internal/faketls/welcome_test.go

 	copy(welcomePacket[11:], empty)
 
 	mac := hmac.New(sha256.New, suite.secret.Key[:])
-	mac.Write(suite.h.Random[:])
-	mac.Write(welcomePacket)
+	mac.Write(suite.h.Random[:]) // nolint: errcheck
+	mac.Write(welcomePacket)     // nolint: errcheck
 
 	suite.Equal(random, mac.Sum(nil))
 }

mtglib/internal/relay/conn_internal_test.go

 
 	suite.tickChannel <- struct{}{}
 
-	suite.c.Read(suite.buf)
+	suite.c.Read(suite.buf) // nolint: errcheck
 }
 
 func (suite *ConnTestSuite) TestWriteOk() {
 
 	suite.tickChannel <- struct{}{}
 
-	suite.c.Write(suite.buf)
+	suite.c.Write(suite.buf) // nolint: errcheck
 }
 
 func (suite *ConnTestSuite) TearDownTest() {