CGContext Drawing two adjacent rhomboids produce a very thin gap, how to reduce it?

The two adjacent rectangle is ok as image below.

override func draw(_ rect: CGRect) {
    // Drawing code
    let leftTop = CGPoint(x:50,y:50)
    let rightTop = CGPoint(x:150,y:100)

    let leftMiddle = CGPoint(x:50,y:300)
    let rightMiddle = CGPoint(x:150,y:300)

    let leftDown = CGPoint(x:50,y:600)
    let rightDown = CGPoint(x:150,y:650)

    let context = UIGraphicsGetCurrentContext()
    context?.addLines(between: [leftTop,rightTop,rightMiddle,leftMiddle])
    UIColor.black.setFill()
    context?.fillPath()

    context?.addLines(between: [leftMiddle,rightMiddle,rightDown,leftDown])
    context?.fillPath()


    let leftTop1 = CGPoint(x:200,y:50)
    let rightTop1 = CGPoint(x:300,y:100)

    let leftMiddle1 = CGPoint(x:200,y:300)
    let rightMiddle1 = CGPoint(x:300,y:350)

    let leftDown1 = CGPoint(x:200,y:600)
    let rightDown1 = CGPoint(x:300,y:650)

    context?.addLines(between: [leftTop1,rightTop1,rightMiddle1,leftMiddle1])
    UIColor.black.setFill()
    context?.fillPath()

    context?.addLines(between: [leftMiddle1,rightMiddle1,rightDown1,leftDown1])
    context?.fillPath()
}

You may need to zoom in to see the gap. If I draw a thin line to cover the gap, then any width may overlap if the color has an alpha channel.

Change shapeColor to let shapeColor = UIColor(white: 0.0, alpha: 0.5) and add context?.setShouldAntialias(false)

from CGContext Drawing two adjacent rhomboids produce a very thin gap, how to reduce it?