Rename test directory to testdata

See https://golang.org/cmd/go/#hdr-Test_packages

CHANGELOG.md

@@ -32,6 +32,7 @@
 - [#783](https://github.com/oauth2-proxy/oauth2-proxy/pull/783) Update Go to 1.15 (@johejo)
 - [#813](https://github.com/oauth2-proxy/oauth2-proxy/pull/813) Fix build (@thiagocaiubi)
 - [#750](https://github.com/oauth2-proxy/oauth2-proxy/pull/750) ci: Migrate to Github Actions (@shinebayar-g)
+- [#829](https://github.com/oauth2-proxy/oauth2-proxy/pull/820) Rename test directory to testdata (@johejo)
 
 # v6.1.1
 

oauthproxy_test.go

@@ -330,7 +330,7 @@ func TestOpenRedirects(t *testing.T) {
 		t.Fatal(err)
 	}
 
-	file, err := os.Open("./test/openredirects.txt")
+	file, err := os.Open("./testdata/openredirects.txt")
 	if err != nil {
 		t.Fatal(err)
 	}