2022-12-03

chapter-1/go_command.go

@@ -0,0 +1,7 @@
+package main
+
+import "fmt"
+
+func main() {
+	fmt.Println("Hello, world!")
+}

chapter-2/01_type_conversions.go

@@ -0,0 +1,12 @@
+package main
+
+import "fmt"
+
+func main() {
+	var x int = 10
+	var y float64 = 30.2
+	var z float64 = float64(x) + y
+	var d int = x + int(y)
+
+	fmt.Println(x, y, z, d)
+}

chapter-2/02_declarations.go

@@ -0,0 +1,19 @@
+// can only use := inside functions (this is nearly always used in functions)
+// := can re-assign vars, as long as one assignment is new
+
+package main
+
+func main() {
+	// declaration list
+	var (
+		x    int
+		y        = 20
+		z    int = 30
+		d, e     = 40, "hello"
+		f, g string
+	)
+
+	// assign values to existing variables
+	a := 10
+	a, b := 20, "hello"
+}

chapter-2/03_const.go

@@ -0,0 +1,33 @@
+// constants are used to give names to literals
+// There is no way to declare that a value is immutable
+// Use constants for hard-coded package level variables
+
+// constants can be typed or untyped
+// leave them untyped for flexibility (can use an untyped int constant in a func that takes a float etc)
+// or hardcode them if needed
+
+package main
+
+import "fmt"
+
+const x int = 10
+
+const (
+	idKey   = "id"
+	nameKey = "name"
+)
+
+const z = 20 * 10
+
+func main() {
+	const y = "hello"
+
+	fmt.Println(x)
+	fmt.Println(y)
+
+	x = x + 1
+	y = "bye"
+
+	fmt.Println(x)
+	fmt.Println(y)
+}

chapter-2/04_unused_variables.go

@@ -0,0 +1,18 @@
+// variables must be read at least once
+// golangci-lint will warn but the compiler will allow it
+
+// package level vars do not need to be read (another reason not to use them)
+
+// constants do not need to be read, if they are not used they are excluded from the build
+
+package main
+
+import "fmt"
+
+func main() {
+	x := 10
+	x = 20
+
+	fmt.Println(x)
+	x = 30
+}

chapter-2/05_naming_variables_constants.go

@@ -0,0 +1,30 @@
+// any unicode letter/number is valid for names in go - don't use them
+
+// snake_case is rarely used, use camelCase
+
+// prefer shorter names, k,v for key,value in for loops etc
+
+// if using single letter var names, you can follow the type. E.g i for int, b for bool
+
+// when naming vars/consts in the package level, favour more descriptive names
+// !!! the smaller the scope of the variable, the shorter the name !!!
+
+package main
+
+import "fmt"
+
+func main() {
+	_0 := 0_0
+	_ᔜ := 20
+	π := 3
+	ａ := "hello" // Unicode U+FF41
+	fmt.Println(_0)
+	fmt.Println(_ᔜ)
+	fmt.Println(π)
+	fmt.Println(ａ)
+
+	ａ = "hello"    // Unicode U+FF41
+	a := "goodbye" // standard lowercase a (Unicode U+0061)
+	fmt.Println(ａ)
+	fmt.Println(a)
+}

go.mod

@@ -0,0 +1,3 @@
+module learning_go
+
+go 1.19