Test Net currently down?

[dh77]

Yes, there were some breaking changes to the Main Net which probably reflected in the Test Net:

Proposer Key Sequence Number Breaking Change

Starting next MainNet Spork (May 26th), when running a transaction, the proposer key sequence number would always be incremented unless any of the following conditions occur: invalid transaction (transaction rejected by collection nodes) any of the transaction signatures are not valid the transaction is missing the signature(s) by the proposer the proposal sequence number is invalid (not match with the one stored on the chain) In other words, the new behavior increments the sequence number ev…

(I somehow overlooked the announcement both on Discord and Flow Forum).
Anyways, you have to update the GO SDK:
go get -u GitHub - onflow/flow-go-sdk: Tools for building Go applications on Flow 🌊

And then probably also run:
go mod download GitHub - golang/protobuf: Go support for Google's protocol buffers
go mod download The Go Programming Language

Hope that helps…