How to convert 2D array to RGB image?

[Xitler]

This is the code using Python:

# Channel01,02,03 are all 2D uint16 arrays with length of 2748*2748.
# The trick here is to convert to gray image firstly,and then merge the gray images into a RGB image...
# I don't know the reason behind it , but it works...
r = Image.fromarray(Channel03*0.1).convert('L')
g = Image.fromarray(Channel02*0.1).convert('L')
b = Image.fromarray(Channel01*0.1).convert('L')
image_output = Image.merge("RGB", (r, g, b))
image_output.save("map_picture.bmp)

I tried to implement the same bahaviour in Go:

    rect := image.Rect(0, 0, 2748, 2748)
    imgSet := image.NewRGBA64(rect)
    for i := 0; i < length; i++ {
        x := i % 2748
        y := i / 2748
        pixel := color.RGBA64{
            // channel1,2,3 are the same with the py code
            R: channel3[i]/10, 
            G: channel2[i]/10,
            B: channel1[i]/10,
            A: 65535,
        }
        imgSet.Set(x, y, pixel)
    }

    outFile, err := os.Create("hybrid.bmp")
    if err != nil {
        t.Error(err)
        return
    }
    defer outFile.Close()
    err = bmp.Encode(outFile, imgSet)
    if err != nil {
        t.Error(err)
        return
    }
}

The comparision result is as following,the image generated by Go seems very lossy…

So,how to obtain the same result using Go?