Remove the custom current user lookup function (#52144)

We added this function to mitigate slow user.Current() calls in
Windows Active Directory environments. Go 1.24 ships with an optimized
verison of user.Current, rendering this utility unnecessary.

Closes #41922

api/utils/user.go

@@ -1,64 +0,0 @@
-/*
-Copyright 2023 Gravitational, Inc.
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
-*/
-
-package utils
-
-import (
-	"os/user"
-	"time"
-
-	"github.com/gravitational/trace"
-)
-
-const lookupTimeout = 10 * time.Second
-
-type userGetter func() (*user.User, error)
-
-type userResult struct {
-	user *user.User
-	err  error
-}
-
-// CurrentUser is just like [user.Current], except an error is returned
-// if the user lookup exceeds 10 seconds. This is because if
-// [user.Current] is called on a domain joined host, the user lookup
-// will contact potentially multiple domain controllers which can hang.
-func CurrentUser() (*user.User, error) {
-	return currentUser(user.Current, lookupTimeout)
-}
-
-func currentUser(getUser userGetter, timeout time.Duration) (*user.User, error) {
-	result := make(chan userResult, 1)
-	go func() {
-		u, err := getUser()
-		result <- userResult{
-			user: u,
-			err:  err,
-		}
-	}()
-
-	timer := time.NewTimer(timeout)
-	defer timer.Stop()
-
-	select {
-	case u := <-result:
-		return u.user, trace.Wrap(u.err)
-	case <-timer.C:
-		return nil, trace.LimitExceeded(
-			"unexpected host user lookup timeout, please explicitly specify the Teleport user with \"--user\" and the host user \"--login\" to skip host user lookup",
-		)
-	}
-}

api/utils/user_test.go

@@ -1,44 +0,0 @@
-/*
-Copyright 2023 Gravitational, Inc.
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
-*/
-
-package utils
-
-import (
-	"os/user"
-	"testing"
-	"time"
-
-	"github.com/gravitational/trace"
-	"github.com/stretchr/testify/require"
-)
-
-func TestCurrentUser(t *testing.T) {
-	t.Parallel()
-
-	u, err := currentUser(func() (*user.User, error) {
-		time.Sleep(100 * time.Millisecond)
-		return nil, nil
-	}, 10*time.Millisecond)
-	require.Nil(t, u)
-	require.Error(t, err)
-	require.True(t, trace.IsLimitExceeded(err))
-
-	u, err = currentUser(func() (*user.User, error) {
-		return nil, nil
-	}, lookupTimeout)
-	require.Nil(t, u)
-	require.NoError(t, err)
-}