Invoker fails to build due to new Go version

[alansong21]

Due to the recent update in the Go version (from 1.18 to 1.21), Invoker fails to build when running make invoker in vSwarm/tools/invoker.

Error message:

        --go_out=. \
        --go_opt="paths=source_relative" \
        proto/helloworld.proto
protoc \
        --go-grpc_out=. \
        --go-grpc_opt="paths=source_relative" \
        proto/helloworld.proto
go mod tidy
go: go.mod file indicates go 1.21, but maximum version supported by tidy is 1.18
make: *** [Makefile:2: invoker] Error 1```

[dhschall]

You have to install upgrade go to version 1.21 and then try again.
https://go.dev/doc/install

# Install new
 rm -rf /usr/local/go && tar -C /usr/local -xzf go1.21.4.linux-amd64.tar.gz
export PATH=$PATH:/usr/local/go/bin