chore: refactor structure

internal/number/number.go

@@ -0,0 +1,16 @@
+package number
+
+import "math"
+
+func Fixed3(num float64) float64 {
+	return fixed(num, 3)
+}
+
+func fixed(num float64, precision int) float64 {
+	output := math.Pow(10, float64(precision))
+	return float64(round(num*output)) / output
+}
+
+func round(num float64) int {
+	return int(num + math.Copysign(0.5, num))
+}