Html2Canvas延迟在渲染图像，而不是在序列

I am having problems with Html2canvas render as i want to take multiple screenshots of an image and send the same to the selected contacts in a sequence but Html2canvas is rendering images in a delayed and unsequential way, which in return is not able to send the image to corresponding selected contact. Below is my code it is running successfully but the delay and unsequential output is creating a lot of problem.I am having problems with Html2canvas render as