When a forward proxy is configured (network_proxy, forward_proxy_url or
HTTP_PROXY), net/http wraps dial errors in a *net.OpError with Op
"proxyconnect". tryAgain used a type assertion to detect DialError, so it
missed the wrapped error and treated it as a failure after the request
was sent. Non-GET requests were then not retried, even though no
connection to the proxy was ever established.
Use errors.As so a DialError is recognized anywhere in the error chain.
Errors that do not contain a DialError are unaffected, so requests that
may have reached the proxy or upstream are still not retried by default.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
