What Happens to Unfinished Goroutines When the Main Goroutine Exits?

Fate of Unfinished Goroutines During Main Goroutine Exit or Return

In the provided sample code, Goroutines are created to handle requests to different servers. The main goroutine, mirroredQuery, returns the fastest response. The question arises: What happens to the unfinished routines (one or two) when mirroredQuery completes?

Abrupt Termination in Main Goroutine Return

When a main goroutine returns, it triggers an abrupt shutdown of the runtime system. This implies that any existing goroutines awaiting communication on an unbuffered or full channel simply vanish without cancellation or termination. They are not actively running or waiting; instead, they cease to exist upon the main goroutine's termination. This phenomenon can be categorized as a goroutine leak, but it is mitigated by the fact that the entire process is terminating.

Continuation of Goroutines During Main Goroutine Runtime

However, if the main goroutine remains active (i.e., not returned), the other goroutines continue operating. They either complete their tasks and return or execute actions that cause a termination. In the given example, the unfinished routines retrieve a response, send it to the channel, and return. These routines evaporate upon completion and return.

Channel Persistence and Resource Leakage

The channel persists after mirroredQuery returns, and it retains the strings received from the goroutines. This could be considered a minor resource leak, particularly in small programs. If no other references exist to the channel, it will eventually be garbage-collected, along with its contents.

Comparison to Unbuffered Channel and Closed Channel

In the case of an unbuffered channel, the "losing" goroutines would block while attempting to send to the full channel. Consequently, these goroutines and the channel itself would persist until program termination. Closing the channel would cause the "losing" goroutines to panic, effectively killing the program. Therefore, using a buffered channel simplifies the code while avoiding these undesirable scenarios.

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