Restructured to have subpackages, added server communication

client/hash.go

@@ -0,0 +1,25 @@
+package main
+
+import (
+	"crypto/sha256"
+	"fmt"
+	"io"
+	"os"
+)
+
+func HashFile(filename string) (string, error) {
+	hashfn := sha256.New()
+
+	infile, err := os.Open(filename)
+	if err != nil {
+		return "", err
+	}
+	defer infile.Close()
+
+	_, err = io.Copy(hashfn, infile)
+	if err != nil {
+		return "", err
+	}
+
+	return fmt.Sprintf("%x", hashfn.Sum(nil)), nil
+}