I was gonna为什么有was可以表示将来时 我将会去做.

过去将来时
过去将来时表示从过去的某一时间来看将来要发生的动作或存在的状态
The Future-in-the-Past Tense
结构：过去将来时由助动词should/would+动词原形构成.
Would常简缩为'd,如I'd,you'd,he'd等；would not常缩写为wouldn't.
提示：注意第一人称用should,其他人称用would
（在美国,甚至在英国,第一人称也常用would）.
用法：过去将来时表示过去某一时间看将要发生的动作或存在的状态.
过去将来时常用在宾语从句中.如：
I didn't know if he would come.
They never knew that population would become a big problem.
She didn't tell me where she would go.
Betty said she would visit the Great Wall next Saturday.
过去将来时也可以用was/were going to +动词原形来表示.如：
I wasn't sure whether she was going to speak at the meeting.
I was sure that they were going to do that.
注：从过去某时看将来要发生的事,还有一些其他的表达形式.
He didn't say when she was coming.
The teacher said that we were having a holiday next Monday.