Add CI workflow to lint and check formatting of Go code

[per1234]

On every push and pull request that affects relevant files, and periodically, lint and check formatting of the
repository's Go module.

[per1234]

There is the remaining go vet error I didn't tackle yet because I'm not knowledgeable about the subject matter:

libraries/db/db.go:213:34: call of json.MarshalIndent copies lock value: arduino.cc/repository/libraries/db.DB contains sync.Mutex

If I'm to guess, it would be this:

diff --git a/libraries/db/db.go b/libraries/db/db.go
index d02bee9..d313367 100644
--- a/libraries/db/db.go
+++ b/libraries/db/db.go
@@ -210,7 +210,7 @@ func (db *DB) Save(r io.Writer) error {
 }

 func (db *DB) save(r io.Writer) error {
-       buff, err := json.MarshalIndent(*db, "", "  ")
+       buff, err := json.MarshalIndent(db, "", "  ")
        if err != nil {
                return err
        }

[silvanocerza]

@per1234 I think this should be the fix, much like in other DB methods.

diff --git a/libraries/db/db.go b/libraries/db/db.go
index d02bee9..d313367 100644
--- a/libraries/db/db.go
+++ b/libraries/db/db.go
@@ -210,7 +210,7 @@ func (db *DB) Save(r io.Writer) error {
 }

 func (db *DB) save(r io.Writer) error {
+	db.mutex.Lock()
+	defer db.mutex.Unlock()
        buff, err := json.MarshalIndent(*db, "", "  ")
        if err != nil {
                return err
        }

I didn't test it though.

[per1234]

Thanks @silvanocerza! Since the go vet violation was not introduced by this PR, but only exposed by it, I'm going to merge this as is. Hopefully the repository can be brought into full compliance in the near future.

---

UPDATE: fixed in #46