The strength of Go is not the language. It's that the libraries you need for web back-end stuff are written, maintained, and used in production by Google. All the obscure cases get exercised in production due to sheer volume of internal usage.

At one time, Go maps were not thread-safe. Was that fixed?

I'd be surprised if the JSON module was used within Google, though. It's neither particularly fast nor particularly convenient nor particularly suited to properly handle edge cases. But it's still in the stdlib for compatibility reasons.

> At one time, Go maps were not thread-safe. Was that fixed?

sync.Map was added, but isn't intended to be a general purpose map.

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The Map type is specialized. Most code should use a plain Go map instead, with separate locking or coordination, for better type safety and to make it easier to maintain other invariants along with the map content.

The Map type is optimized for two common use cases: (1) when the entry for a given key is only ever written once but read many times, as in caches that only grow, or (2) when multiple goroutines read, write, and overwrite entries for disjoint sets of keys. In these two cases, use of a Map may significantly reduce lock contention compared to a Go map paired with a separate Mutex or RWMutex.

Exactly, by Google.