go: Fix things staticcheck complains about

Client: go

Staticcheck is the recommended replacement of the frozen and deprecated
official golint linter [1].

Fix the things it complained about (or add lint:ignore directive) in:

- lib/go/thrift
- lib/go/test/tests
- tutorial/go/src
- test/go/src
- compiler generated code

The majority of the fixes are in the following categories:

- Use of deprecated function (mainly the TConfiguration related ones)
- Redundant break in switch cases
- Unused and unexported variables/fields/functions

Also in the same spirit as fb539ae, remove the error return from
NewTSSLSocket as it can never be non-nil.

This change will be cherry-picked into 0.15.0 branch after merged.

[1]: https://groups.google.com/g/golang-nuts/c/rCP70Aq_tBc
diff --git a/test/go/src/common/clientserver_test.go b/test/go/src/common/clientserver_test.go
index d5e3c43..609086b 100644
--- a/test/go/src/common/clientserver_test.go
+++ b/test/go/src/common/clientserver_test.go
@@ -49,7 +49,6 @@
 }
 
 func TestAllConnection(t *testing.T) {
-	certPath = "../../../keys"
 	wg := &sync.WaitGroup{}
 	wg.Add(len(units))
 	for _, unit := range units {
@@ -67,6 +66,9 @@
 	handler := NewMockThriftTest(ctrl)
 
 	processor, serverTransport, transportFactory, protocolFactory, err := GetServerParams(unit.host, unit.port, unit.domain_socket, unit.transport, unit.protocol, unit.ssl, "../../../keys", handler)
+	if err != nil {
+		t.Errorf("GetServerParams failed: %v", err)
+	}
 
 	server := thrift.NewTSimpleServer4(processor, serverTransport, transportFactory, protocolFactory)
 	if err = server.Listen(); err != nil {