add ctx to blocksItr

[cendhu]

Type of change

• Bug fix
• Improvement (improvement to code, performance, etc)

Description

Add context.Context to the block iterator so that waitForBlock respects context cancellation. This fixes goroutine leaks in callers like deliver.go where cursor.Next() blocks indefinitely even after the gRPC stream's context is cancelled.

[liran-funaro]

The iterator does not have to hold the context in this case.
Instead, it.Next() should accept a context parameter, which is propagated downwards on a per call basis.
I suggest a re-work on the basis on the above claim.

[cendhu]

The iterator does not have to hold the context in this case.
Instead, it.Next() should accept a context parameter, which is propagated downwards on a per call basis.
I suggest a re-work on the basis on the above claim.

I know. I went with the current design based on the following:

1. Throughout the iterator lifetime, the ctx would not change.
2. I did not want to make a significant changes.

I don't mind adding ctx to the Next().

[liran-funaro]

@cendhu Will introducing context to it.Next() will result in a major diff?

[cendhu]

@cendhu Will introducing context to it.Next() will result in a major diff?

I expected so but It does not seem to be true given I making the changes. In fact, lesser number of changes.