/jmbag, /sum, /multiply, /fetch realizirani po specifikaciji

• throws 404: File not yet created
• Write to file: Send json in POST body, e.g. {"ime": "Ivan", "prezime": "Horvat", "JMBAG": "0036391234"}
• Read: response to GET is of type text/plain

• Vector size: const N uint
• POST data to server in form of JSON:

        {
           "a":{
             "0": 2
           },
           "x": {
             "0": 1,
             "1": 2,
             "2": -3
           },
           "y": {
             "0": 1,
             "1": 1,
             "2": 1
           }
        }

• throws 400: JSON Format Error and 400: X or Y index greater than N
• Parallelism achieved using WaitGroup and RWMutex
• SAXPY calculated with gonum.org/v1/gonum module

$ go build -race
$ ./zadatak