* all: use sort.Strings when applicable
Basically, sort.Strings is the shortcut of Sort(StringSlice(a)) but its
more readable.
* all: replace string(bytes.Buffer.Bytes()) with bytes.Buffer.String()
Although its only occured on test files, it may be worth to simplified it.
* http_test: simplify strings.Index with strings.Contains
Both have the same O(n), but strings.Contains more readable on
if-condition.
* args: simplify if-condition check on boolean value
* all: simplify variable initialization
If we assign the variable after declaring it, we can simplify it using
":=" operator or "= value".
The reader can still known the type of variable from the struct name or
variable type before assignment operator.