feat: add insertion sort

Author: codejsha

README.md

@@ -1196,7 +1196,7 @@ list.sort(Comparator.comparingInt(String::length));
 | **Worst**   |    $O(n log n)$     |             |
 | **Average** |    $O(n log n)$     |             |
 
-- Insertion sort, CLRS#2.1: [cpp](/cpp-algorithm/src/sort/sort.h), [java](/java-algorithm/src/main/java/com/example/algorithm/sort/InsertionSort.java) | Insertion sort is a comparison-based sorting algorithm that builds the final sorted array one element at a time. One of the fastest algorithms for sorting very small arrays (around 10 elements).<br>($\textit{n}$ is the number of elements)
+- Insertion sort, CLRS#2.1: [cpp](/cpp-algorithm/src/sort/sort.h), [golang](go-algorithm/pkg/sort/insertion_sort.go), [java](/java-algorithm/src/main/java/com/example/algorithm/sort/InsertionSort.java) | Insertion sort is a comparison-based sorting algorithm that builds the final sorted array one element at a time. One of the fastest algorithms for sorting very small arrays (around 10 elements).<br>($\textit{n}$ is the number of elements)
 
 | **Case**    | **Time complexity** | **Remarks**                                                                     |
 | ----------- | :-----------------: | ------------------------------------------------------------------------------- |

go-algorithm/pkg/sort/insertion_sort.go

@@ -0,0 +1,17 @@
+package sort
+
+import (
+	"golang.org/x/exp/constraints"
+)
+
+func insertionSort[T constraints.Integer](arr []T) {
+	for i := 0; i < len(arr); i++ {
+		key := arr[i]
+		j := i - 1
+		for j >= 0 && arr[j] > key {
+			arr[j+1] = arr[j]
+			j--
+		}
+		arr[j+1] = key
+	}
+}

go-algorithm/pkg/sort/insertion_sort_test.go

@@ -0,0 +1,41 @@
+package sort
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"golang.org/x/exp/constraints"
+)
+
+func Test_insertionSort(t *testing.T) {
+	type args[T constraints.Integer] struct {
+		arr []T
+	}
+	type testCase[T constraints.Integer] struct {
+		name string
+		args args[T]
+		want []T
+	}
+	tests := []testCase[int]{
+		{
+			name: "Integer Case",
+			args: args[int]{
+				arr: []int{31, 64, 49, 85, 71, 26, 6, 19},
+			},
+			want: []int{6, 19, 26, 31, 49, 64, 71, 85},
+		},
+		{
+			name: "Empty array input",
+			args: args[int]{},
+			want: nil,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			insertionSort(tt.args.arr)
+
+			assert.Equalf(t, tt.want, tt.args.arr, "insertionSort() got = %v, want %v", tt.args.arr, tt.want)
+		})
+	}
+}