bump minimum version of go used to build cli

[techknowlogick]

Due to the CLI setting go.mod to go1.16 building the CLI fails due to modules requiring a newer version of go.

Errors received:

# golang.org/x/sys/unix
vendor/golang.org/x/sys/unix/syscall.go:83:16: unsafe.Slice requires go1.17 or later (-lang was set to go1.16; check go.mod)
vendor/golang.org/x/sys/unix/syscall_darwin.go:95:8: unsafe.Slice requires go1.17 or later (-lang was set to go1.16; check go.mod)
vendor/golang.org/x/sys/unix/syscall_unix.go:118:7: unsafe.Slice requires go1.17 or later (-lang was set to go1.16; check go.mod)
vendor/golang.org/x/sys/unix/sysvshm_unix.go:33:7: unsafe.Slice requires go1.17 or later (-lang was set to go1.16; check go.mod)

This PR is the result of bumping go.mod to go1.17, and running go mod tidy

Note: I am running into this error because I am attempting to package the CLI for NixOS, which has a specific way of building software to ensure reproducible builds.

[tasn]

Thanks, the team will take a look!

[techknowlogick]

Hi @tasn, would you, or someone else at svix, be able to poke at this PR?