Add Combine Two Slices as a Go TIL

go/combine-two-slices.md

@@ -0,0 +1,51 @@
+# Combine Two Slices
+
+The `append` function can be used to create a new slice with the contents of
+the given slice and one or more items added to the end.
+
+We can add one or more items like so:
+
+```go
+s1 := []int{1, 2, 3, 4}
+s2 := append(s1, 5)
+s3 := append(s2, 6, 7, 8)
+
+fmt.Println(s1) //=> [1 2 3 4]
+fmt.Println(s2) //=> [1 2 3 4 5]
+fmt.Println(s3) //=> [1 2 3 4 5 6 7 8]
+```
+
+But what if we have a second slice instead of individual items? We could import
+`slices` and use its `Concat` function. Or we can stick with `append` and
+unpack that slice as a series of arguments into the second part of `append`
+using `slice...`.
+
+```go
+s4 := append(s2, s1...)
+fmt.Println(s4) //=> [1 2 3 4 5 1 2 3 4]
+```
+
+Here is the full example:
+
+```go
+package main
+
+import (
+	"fmt"
+)
+
+func main() {
+	s1 := []int{1, 2, 3, 4}
+	s2 := append(s1, 5)
+	s3 := append(s2, 6, 7, 8)
+
+	fmt.Println(s1)
+	fmt.Println(s2)
+	fmt.Println(s3)
+
+	s4 := append(s2, s1...)
+	fmt.Println(s4)
+}
+```
+
+[source](https://pkg.go.dev/builtin#append)