Atomic loads need to be aligned

[nhooyr]

See https://golang.org/pkg/sync/atomic/#pkg-note-BUG

On ARM, x86-32, and 32-bit MIPS, it is the caller's responsibility to arrange for 64-bit alignment of 64-bit words accessed atomically. The first word in a variable or in an allocated struct, array, or slice can be relied upon to be 64-bit aligned.

Was reported to me by @andersfylling on reddit.