Ask HN: Best resources for learning FPGA programming in 2019?

I'm an experienced software engineer that's done mostly backend development in C# and web development using PHP and various javascript stacks. I'm familiar with c/c++, assembly language and embedded systems (through some CS courses and more recently playing Shenzen I/O).

My long-term aim is to utilize FPGA acceleration in machine learning contexts. What would be my best resources to start learning?