refactor: rename files to follow Go convention

testdata/var_naming_test.go

@@ -0,0 +1,12 @@
+// Test for name linting.
+
+// Package pkg_with_underscores ...
+package varnaming_test
+
+var var_name int // MATCH /don't use underscores in Go names; var var_name should be varName/
+
+func Test_ATest()           {}
+func Example_AnExample()    {}
+func Benchmark_ABenchmark() {}
+
+func Fuzz_AFuzz() {}