Go By Example 1

Learning to go

import (
	"encoding/json"
	"fmt"
	"strconv"
	"strings"
)

a := [7]string{"sun", "mon", "tues", "wednes", "thurs", "fri", "satur"}

res := make([]string, 0)
for i := range a {
		s := "DAY " + strconv.Itoa(i) + ": " + strings.Title(a[i]) + "day"
		res = append(res, s)
}

resB, _ := json.Marshal(res)
fmt.Println(string(resB))

  • First, we declare a new array a of type [7]string, which means it can hold 7 string values. We also initialize it with the values of a partial name of days.

  • Then, we create a new slice with a length of 0 and a capacity of 0.

  • Then we use range to iterate over elements in the array a. As we don't need the value for each entry, we ignore the second argument and only specify the index i.

  • Within the for loop, we declare and initialize a string with a formatted message, which would print something like "Day 1: Sunday". We use the Itoa function from the strconv package to convert an integer to string type, to allow the concatenation of two data structures (int and string). We also use a function in the built-in strings package to capitalize each day.

  • Then, we use the append function, which does not modify the slice in place. Instead, it returns a new slice with the appended element(s). In order to append an element to the res slice, we will need to assign the returned slice back to the res variable. So we call the append function with the slice and the s variable as separate arguments.

  • Then, we exit the loop and move on. To encode data in json, we use the json.Marshal function to convert the res slice into a JSON byte slice ([]byte). The _ is known as the "blank identifier" and is used to discard the second return value of the json.Marshal function, which is an error value. If the function succeeds, the error value will be nil, so discarding it is safe in this case.

  • Lastly, we convert the resB byte slice into a string and prints it to the console using the fmt.Println function. The output will be a JSON-formatted string representation of the resB slice, like so:

make run

["DAY 0: Sunday","DAY 1: Monday","DAY 2: Tuesday","DAY 3: Wednesday","DAY 4: Thursday","DAY 5: Friday","DAY 6: Saturday"]

To me, learning go is like learning how to express an abstract idea or an instruction in one line. However, if we want to go deep (pun intended :D), we should be able to expand this compact form into a narrative that is easy to follow.