Tidy up blog sample 2021-01-20-logging

[nightroman]

• fix build error (missed using)
• deal with nullable warnings
• remove not used packages

[nightroman]

Anyone interested? Otherwise I am going to close, do not like it hanging in my TODO list :)

[PascalSenn]

@pkellner Do you want to have a look at this? :)

[pkellner]

I have no issues. Not sure is static matters. I'm sure I copied an example from place in the mini profiler repo.

[nightroman]

Let me make _miniProfiler the instance field and see if it's OK.

[nightroman]

Done, _miniProfiler is the instance field, it works this way with no issues. Also used is not null instead of != null for consistency.

[nightroman]

Not sure is static matters. I'm sure I copied an example from place in the mini profiler repo.

In theory static may start to misbehave in some realistic scenarios with concurrent requests.

[PascalSenn]

if @pkellner approves we can get it merged :) It's his blogpost so he should have the control over what changes go in :)

[pkellner]

I'm good.

[nightroman]

I'm good.

@PascalSenn Let's merge and move on :)