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June 1st 2020
Last Modified


Functions for loading root certificates for TLS connections.

Go’s standard library crypto/tls provides a common mechanism for configuring TLS connections in tls.Config. The RootCAs field on this struct is a pool of certificates for the client to use as a trust store when verifying server certificates.

This library contains utility functions for loading certificates destined for that field, as well as one other important thing:

When the RootCAs field is nil, the standard library attempts to load the host’s root CA set. This behavior is OS-specific, and the Darwin implementation contains a bug that prevents trusted certificates from the System and Login keychains from being loaded. This library contains Darwin-specific behavior that works around that bug.

Example Usage

Here’s a snippet demonstrating how this library is meant to be used:

func httpClient() (*http.Client, error)
	tlsConfig := &tls.Config{}
	err := rootcerts.ConfigureTLS(tlsConfig, &rootcerts.Config{
		CAFile:        os.Getenv("MYAPP_CAFILE"),
		CAPath:        os.Getenv("MYAPP_CAPATH"),
		CACertificate: []byte(os.Getenv("MYAPP_CERTIFICATE")),
	if err != nil {
		return nil, err
	c := cleanhttp.DefaultClient()
	t := cleanhttp.DefaultTransport()
	t.TLSClientConfig = tlsConfig
	c.Transport = t
	return c, nil