Comment by AaronFriel

It's often a good idea when the application has its own buffering, as is common in many languages and web frameworks which implement some sort of 'reader' interface which can alternate symbols of "chunks" and "flushes" or only emit entire payloads (a single chunk). With scatter-gather support for IO, it's generally OK for the application to produce small chunks followed by a flush. Those application layer frameworks want Nagle's algorithm turned off at the TCP layer to avoid double-buffering and incurring extra latency.

Go however is disabling Nagle's by default as opposed to letting it be a framework level decision.