The Building Blocks

The Building Blocks

The Building Blocks

Every value in Go has a type. These four cover most of what you'll write:

Type What it holds Example
int Integers 42, -7, 0
float64 Decimals 3.14, 0.5
string Text (in quotes) "hello", "Go"
bool True or false true, false

You can do math with numbers, compare them, and glue strings together:

example.go
fmt.Println(10 + 3)       // 13
fmt.Println(10 > 3)       // true
fmt.Println("Go" + "lang") // Golang
fmt.Println(7.0 / 2.0)    // 3.5

Comparisons (>, <, >=, <=, ==, !=) always produce a bool. The + operator adds numbers or joins strings.

Spaces when printing multiple values

fmt.Println inserts a space between each argument. + joins strings with nothing between them. If your string already ends in a space and you then use a comma, you get two spaces:

example.go
fmt.Println("a", "b")           // a b
fmt.Println("a" + "b")          // ab
fmt.Println("Status: ", "OK")   // Status:  OK   (two spaces)
fmt.Println("Status: " + "OK")  // Status: OK    (one space)

Two Things Go Won't Let You Do

  • Mixing types. You can't add an int to a float64, or a number to a string. The compiler catches it before your code runs.
  • Unused variables. Every declared variable must be used, or the compiler stops with an error like declared and not used.
>_Exercise

Exercise: Health Check

You're building an API health endpoint. Fill in the three fmt.Println calls so the output matches:

example.go
Status: OK
Healthy: true
Latency: 1.5

Each line uses a different technique:

  1. Status - join two strings with +
  2. Healthy - use == to compare statusCode to 200 (this produces a bool)
  3. Latency - divide two floats to get 1.5
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Key Takeaway
Next UpStoring values so you can use them later.
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