(I scanned through issues with go.dev: and didn't see anything like this, forgive me if I missed any.)

What is the URL of the page with the issue?

https://pkg.go.dev/github.com/CloudyKit/jet?tab=doc

What is your user agent?

Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.122 Safari/537.36

Screenshot

What did you do?

Visit the page

What did you expect to see?

What did you see instead?

A variety of style changes, mainly font-related, that in my opinion (stated as such) are not improvements, and which make the documentation harder to read.

• The existing font stack for godoc gives me Helvetica Neue for most text, and Menlo for the code/monoscape stuff (I am on a Mac). To me, Roboto and Source Code Pro are not as readable, and are a jarring change. Work Sans is actually not bad and possibly an improvement for where it's used.
• In the Index up top, (shown in screenshot) the fonts are bigger (~4px?) which fits less on the screen, makes all of the text seem higher up the importance hierarchy, and goes counter to its purpose as a summary/definition-overview of the interface of the package.
• In the Index, we lost the bullet points next to the methods. They are "plain", sure, but they made the Index more structured, made it easier to separate the levels when you scan through with your eye.
• The content width got significantly larger, from 698px in my browser to 960. In my opinion this is too wide to be easily readable. Compare to these GitHub Issues at 639, Google's homepage snippets at 600, Medium at 680, SwiftDoc.org at 847, even the fairly wide GitHub readmes at 882! I get that these exact numbers are subjective and probably related to my screen size and various other factors, but the point is that it's a lot bigger, and the increased width hurts readability.
• In the main body of the docs, the methods are the same size as the types. In existing godoc, types are 24px and methods are 18px, so when you're scanning through it's easy to visually separate them. In pkg.go.dev they're both 24px.
• Fonts are generally just larger, so between that and the content size increase the page feels like it's shouting at me in comparison to the old one.

Suggestions

Again, these are all my opinions, but since you are asking for feedback, I would suggest:

• Please return the font stack to use Helvetica Neue and Menlo where Godoc used it.
• Please reduce the content width closer to the existing Godoc; if it needs to increase a little I understand, but even ~800px would be much better than 960. If you need to keep the overall content width because of other panes in the tab bar, some horizontal padding on the doc pane would work fine.
• Please return the bullet points next to methods in the Index.
• Please reduce font sizes, perhaps in general, but specifically the Index font size and the sizes of method signatures in the main body of documentation. A general review to ensure that the typography is communicating the hierarchy of data might not be a bad idea.

In closing, godoc.org is fantastic! I would suggest we slavishly copy it unless the Go Team is getting a lot of requests to change it (which you might, I don't know).