crypto/tls: TestServerHandshakeContextCancellation failure with "Socket is not connected" on js-wasm

[bcmills]

2021-03-19T19:59:56-3b0d288/js-wasm

--- FAIL: TestServerHandshakeContextCancellation (0.00s)
    handshake_server_test.go:1975: Unexpected server handshake error: write tcp 127.0.0.1:1->127.0.0.1:228: Socket is not connected
    handshake_server_test.go:1981: conn.Close does not error as expected when called multiple times on WASM
FAIL
FAIL	crypto/tls	8.362s

It isn't obvious to me whether this is the same underlying problem as #45299 and/or #45106 (CC @johanbrandhorst)

[bcmills]

Also seen on a TryBot: https://storage.googleapis.com/go-build-log/e31d7a76/js-wasm_498d5646.log

[johanbrandhorst]

With #45106 resolved, hopefully it should tell us whether this is the same bug.

[gopherbot]

Timed out in state WaitingForInfo. Closing.

(I am just a bot, though. Please speak up if this is a mistake or you have the requested information.)