diff --git a/go/study/base/go.mod b/go/study/base/go.mod
new file mode 100644
index 00000000..6792fc39
--- /dev/null
+++ b/go/study/base/go.mod
@@ -0,0 +1,3 @@
+module github.com/tecyokomichi/WebAppLearning/go/study/base
+
+go 1.16
diff --git a/go/study/base/main.go b/go/study/base/main.go
new file mode 100644
index 00000000..1aa29b2c
--- /dev/null
+++ b/go/study/base/main.go
@@ -0,0 +1,24 @@
+package main
+
+import "fmt"
+
+func main() {
+	p1 := &Point{Px: 100, Py: 50}
+	fmt.Printf("%#v\n", p1)
+
+	c1 := NewCircle(p1, 30)
+	fmt.Printf("%#v\n", c1)
+	fmt.Printf("面積：　%#v\n", c1.Area())
+	c1.Expand(10)
+	fmt.Printf("%#v\n", c1)
+
+	r1 := &Rect{Point: p1, width: 20, length: 10}
+	fmt.Printf("面積：　%#v\n", r1.Area())
+	r2 := &Rect{Point: p1, width: 30, length: 20}
+	r3 := &Rect{Point: p1, width: 40, length: 30}
+	r4 := &Rect{Point: p1, width: 50, length: 40}
+	r5 := &Rect{Point: p1, width: 10, length: 5}
+	fmt.Printf("%#v\n", r1)
+	fmt.Printf("%#v\n", RecList([]*Rect{r1, r2, r3, r4, r5}).Biggest())
+	fmt.Printf("%#v\n", Shapes([]Shape{c1, r1, r2, r3, r4, r5}).Biggest())
+}
diff --git a/go/study/base/main_test.go b/go/study/base/main_test.go
new file mode 100644
index 00000000..859e9d68
--- /dev/null
+++ b/go/study/base/main_test.go
@@ -0,0 +1,42 @@
+package main
+
+import "testing"
+
+func TestNewCircle(t *testing.T) {
+	p := &Point{Px: 100, Py: 200}
+	c := NewCircle(p, 300)
+	if c.radius != 300 {
+		t.FailNow()
+	}
+}
+
+func TestExpandCircle(t *testing.T) {
+	p := &Point{Px: 100, Py: 200}
+	c := NewCircle(p, 300)
+	c.Expand(400)
+	if c.radius != 700 {
+		t.FailNow()
+	}
+}
+
+func TestArea(t *testing.T) {
+	p := &Point{Px: 100, Py: 200}
+	r := &Rect{Point: p, width: 300, length: 400}
+	if r.Area() != 120000 {
+		t.FailNow()
+	}
+}
+
+func TestBiggest(t *testing.T) {
+	p := &Point{Px: 100, Py: 200}
+	c := NewCircle(p, 300)
+	r1 := &Rect{Point: p, width: 300, length: 400}
+	r2 := &Rect{Point: p, width: 30, length: 40}
+	r3 := &Rect{Point: p, width: 3, length: 4}
+	if RecList([]*Rect{r1, r2, r3}).Biggest().Area() != 120000 {
+		t.FailNow()
+	}
+	if Shapes([]Shape{c, r1, r2, r3}).Biggest().Area() < 282743 || Shapes([]Shape{c, r1, r2, r3}).Biggest().Area() > 282744 {
+		t.FailNow()
+	}
+}
diff --git a/go/study/base/struct.go b/go/study/base/struct.go
new file mode 100644
index 00000000..448f1785
--- /dev/null
+++ b/go/study/base/struct.go
@@ -0,0 +1,61 @@
+package main
+
+import "math"
+
+type Point struct {
+	Px, Py int
+}
+
+type Shape interface {
+	Area() float64
+}
+
+type Circle struct {
+	radius int
+	Point  *Point
+}
+
+type Rect struct {
+	width, length int
+	Point  *Point
+}
+
+func NewCircle(p *Point, r int) *Circle {
+	return &Circle{Point: p, radius: r}
+}
+
+func (c *Circle) Expand(dr int){
+	c.radius += dr
+}
+
+func (c *Circle) Area() float64 {
+	return float64(c.radius * c.radius) * math.Pi
+}
+
+func (r *Rect) Area() float64 {
+	return float64(r.width * r.length)
+}
+
+type RecList []*Rect
+
+func (rl RecList) Biggest() *Rect {
+	var b *Rect
+	for _, r := range rl {
+		if b == nil || r.Area() > b.Area(){
+			b = r
+		}
+	}
+	return b
+}
+
+type Shapes []Shape
+
+func (sha Shapes) Biggest() Shape {
+	var b Shape
+	for _, r := range sha {
+		if b == nil || r.Area() > b.Area(){
+			b = r
+		}
+	}
+	return b
+}