package main

import (
    "fmt"
    "strconv"
    "math/big"
    "github.com/shopspring/decimal"
)

func main() {
    //32位浮点，错误
    var a1,b1,c1 float32
    a1 = 1.69
    b1 = 1.7
    c1 = a1*b1
    fmt.Println(c1)

    //64位浮点，错误
    var a2,b2,c2 float64
    a2 = 1.69
    b2 = 1.7
    c2 = a2 * b2
    fmt.Println(c2)

    //大数据浮点，错误
    a3 := new(big.Float).SetFloat64(1.69)
    b3 := new(big.Float).SetFloat64(1.7)
    c3 := new(big.Float).Mul(a3, b3)
    fmt.Println(c3)

    //高精度，正确
    a4 := decimal.NewFromFloat(1.69)
    b4 := decimal.NewFromFloat(1.7)
    c4 := a4.Mul(b4)
    fmt.Println(c4)

    //四舍五入，正确
    var f float32
    f = 2.872999999
    //精度小数点后4位
    s := fmt.Sprintf("%.4f", f)
    float, _ := strconv.ParseFloat(s, 32)
    f = float32(float)
    fmt.Println(f)
}

输出：

2.8730001
2.8729999999999998
2.8729999999999998
2.873
2.873