I think we prefer to say: Jīntiān wǒ xuéwán le wǒde kèchéng. Jīntiān wǒ de kèchéng jiéshù le. Note:wánchéng is a little bit formal, like in a report or news. In oral, we commonly use "v.+wán". Jiéshù can be used when the subject is the thing. Some time you could see "sb.+ jiéshù+sth." but that means sb. finish it on purpose because they don't want anymore.

My advice: jin1 tian1 wo3 wan2cheng2 le wo3 de ke4cheng2. This one is the best. jie2shu4 is closer to the English word, "end". (Hope it helps. :) )

Today I finished my course. Jin1 tian1 wo3 wan2cheng2 wo3 de ke4 cheng2 le. Wo du wanliao wo de kecheng. jie shu. --- If that class is your last one, you can use'jie shu wo de ke cheng le' Ohterwise, 'wancheng' and 'du wan liao' are much suitable.