Method GetRequestMetadata

credentials/sts/sts.go:152–182

GetRequestMetadata returns the cached accessToken, if available and valid, or fetches a new one by performing an STS token exchange.

(ctx context.Context, _ ...string)

// GetRequestMetadata returns the cached accessToken, if available and valid, or
// fetches a new one by performing an STS token exchange.
func (c *callCreds) GetRequestMetadata(ctx context.Context, _ ...string) (map[string]string, error) {
	ri, _ := credentials.RequestInfoFromContext(ctx)
	if err := credentials.CheckSecurityLevel(ri.AuthInfo, credentials.PrivacyAndIntegrity); err != nil {
		return nil, fmt.Errorf("unable to transfer STS PerRPCCredentials: %v", err)
	}

	// Holding the lock for the whole duration of the STS request and response
	// processing ensures that concurrent RPCs don't end up in multiple
	// requests being made.
	c.mu.Lock()
	defer c.mu.Unlock()

	if md := c.cachedMetadata(); md != nil {
		return md, nil
	}
	req, err := constructRequest(ctx, c.opts)
	if err != nil {
		return nil, err
	}
	respBody, err := sendRequest(c.client, req)
	if err != nil {
		return nil, err
	}
	ti, err := tokenInfoFromResponse(respBody)
	if err != nil {
		return nil, err
	}
	c.tokenMetadata = map[string]string{"Authorization": fmt.Sprintf("%s %s", ti.tokenType, ti.token)}
	c.tokenExpiry = ti.expiryTime
	return c.tokenMetadata, nil
}

// RequireTransportSecurity indicates whether the credentials requires
// transport security.