Update Go versions used in travis and LANGUAGES.md

Per our support policy, drop support of go 1.16 and add support of go
1.18.

Also enable go vet in make check, and fix issues reported by go vet.
diff --git a/test/go/Makefile.am b/test/go/Makefile.am
index d7db957..ef00df3 100644
--- a/test/go/Makefile.am
+++ b/test/go/Makefile.am
@@ -19,6 +19,12 @@
 
 BUILT_SOURCES = gopath
 
+if GOVERSION_GE_118
+GOINSTALLEXTRA = -buildvcs=false
+else
+GOINSTALLEXTRA =
+endif
+
 THRIFTCMD = $(THRIFT) -out src/gen --gen go:thrift_import=github.com/apache/thrift/lib/go/thrift,package_prefix=github.com/apache/thrift/test/go/src/gen/$(COMPILER_EXTRAFLAG)
 THRIFTTEST = $(top_srcdir)/test/ThriftTest.thrift
 
@@ -37,13 +43,13 @@
 	touch gopath
 
 bin/testclient: gopath
-	GOPATH=`pwd` $(GO) install -mod=mod ./src/bin/testclient
+	GOPATH=`pwd` $(GO) install $(GOINSTALLEXTRA) -mod=mod ./src/bin/testclient
 
 bin/testserver: gopath
-	GOPATH=`pwd` $(GO) install -mod=mod ./src/bin/testserver
+	GOPATH=`pwd` $(GO) install $(GOINSTALLEXTRA) -mod=mod ./src/bin/testserver
 
 bin/stress: gopath
-	GOPATH=`pwd` $(GO) install -mod=mod ./src/bin/stress
+	GOPATH=`pwd` $(GO) install $(GOINSTALLEXTRA) -mod=mod ./src/bin/stress
 
 clean-local:
 	$(RM) -r src/gen src/github.com/golang src/thrift bin pkg gopath ThriftTest.thrift