How I Write HTTP Clients

A practical walkthrough of patterns for building HTTP API clients in Go, using an Infogram API client as a concrete example. Covers five key concepts: composing client options with a configurable struct (custom http.Client, endpoint, credentials), implementing custom JSON marshaling/unmarshaling for non-standard types like url.URL, HMAC-based HTTP request signing, creating small composable convenience methods backed by a shared Do() helper, and returning binary responses as io.Reader for PDF/PNG/HTML formats. The approach emphasizes testability via httptest.Server injection and keeping endpoint methods minimal by centralizing boilerplate.