Enabled maligned, staticcheck and errcheck linters (#206)

* Enabled maligned check

* Enabled staticcheck

* Fixes for golint

* Enabled errcheck linter

* Added fixes for error check

* Added errcheck for tests

* Fixed test

* Increased golangci-lint deadline for travis

* Increased golangci-lint deadline for travis

* Decreased golangci-lint deadline for travis

* Revert for backward compatibility

* Using log.Println() instead of fmt.Println()

* Handling os.RemoveAll() errors

* Using t.Error(error) instead of t.Errorf("%v", err)

* Using t.Fatal(error) instead of t.Fatalf("%v", err)

* Using fmt.Sprint(sum) instead of t.Srintf("%v", sum)

* Refactoring

* Revert for backward compatibility

* Revert

* go mod tidy

* Added error logging

* Added error logging

* Added error handling

* Added error handling

* Added error logging

* Fix error logging

* Added error handling

* Fix

* Added logging for migr.Buffer()

* Fixes

* Firebird test disabled

* Fixed nolint comment

* Updated firebird docker image version

* Disabled test for firebird 2.5

* Fixed // nolint

database/spanner/spanner_test.go

@@ -24,7 +24,7 @@ func Test(t *testing.T) {
 	addr := fmt.Sprintf("spanner://%s", db)
 	d, err := s.Open(addr)
 	if err != nil {
-		t.Fatalf("%v", err)
+		t.Fatal(err)
 	}
 	dt.Test(t, d, []byte("SELECT 1"))
 }
@@ -43,11 +43,11 @@ func TestMigrate(t *testing.T) {
 	addr := fmt.Sprintf("spanner://%s", db)
 	d, err := s.Open(addr)
 	if err != nil {
-		t.Fatalf("%v", err)
+		t.Fatal(err)
 	}
 	m, err := migrate.NewWithDatabaseInstance("file://./examples/migrations", db, d)
 	if err != nil {
-		t.Fatalf("%v", err)
+		t.Fatal(err)
 	}
 	dt.TestMigrate(t, m, []byte("SELECT 1"))
 }