Good luck

go.mod

@@ -0,0 +1,3 @@
+module somename
+
+go 1.17

solution.go

@@ -1,12 +1,27 @@
 package square
 
-// Define custom int type to hold sides number and update CalcSquare signature by replacing #yourTypeNameHere#
 
-// Define constants to represent 0, 3 and 4 sides.  Test uses mnemos: SidesTriangle(==3), SidesSquare(==4), SidesCircle(==0)
-// it's like:
-// CalcSquare(10.0, SidesTriangle)
-// CalcSquare(10.0, SidesSquare)
-// CalcSquare(10.0, SidesCircle)
+import (
+	"math"
+)
 
-func CalcSquare(sideLen float64, sidesNum #yourTypeNameHere#) float64 {
+type SidesNumber int
+
+const (
+	SidesCircle   SidesNumber = 0
+	SidesTriangle SidesNumber = 3
+	SidesSquare   SidesNumber = 4
+)
+
+func CalcSquare(sideLen float64, sidesNum SidesNumber) float64 {
+	switch sidesNum {
+	case SidesTriangle:
+		return (sideLen * sideLen * math.Sqrt(3) / 4)
+	case SidesSquare:
+		return (sideLen * sideLen)
+	case SidesCircle:
+		return (math.Pi * sideLen * sideLen)
+	default:
+		return (0)
+	}
 }