"If you have tons of depedencies then it's not feasible to check every diff."
Part of bringing in a dependency is bringing in the responsibility for verifying it's not obviously being used badly. One of the things I've come to respect the Go community for is its belief that dependencies are more expensive that most developers currently realize, and so generally library authors try to minimize dependencies. Our build systems make it very easy to technically bring in lots of dependencies, but are not currently assisting us in maintaining them properly very often. (In their defense, it is not entirely clear to me what the latter would even mean at an implementation level. I have some vague ideas, but nothing solid enough to complain about not having when even I don't know what it is I want exactly.)
I've definitely pulled some things in that pulled in ~10 other dependencies, but after inspection, they were generally all very reasonable. I've never pulled a Go library and gotten 250 dependencies pulled in transitively, which seems to be perfectly normal in the JS world.
I won't deny I haven't auditing every single line of every single dependency... but I do look at every incoming patch when I update. It's part of the job. (And I have actually looked at the innards of a fairly significant number of the dependencies.) It's actually not that hard... malicious code tends to stick out like a sore thumb. Not always [1], but the vast majority of the time. In static languages, you see things like network activity happening where it shouldn't, and in things like JS, the obfuscation attempts themselves have a pretty obvious pattern to them (big honking random-looking string, fed to a variety of strange decoding functions and ultimately evaluated, very stereotypical look to it).
And let me underline the point that there's a lot of tooling right now that actively assists you into getting into trouble on this front, but doesn't do much to help you hold the line. I'm not blaming end developers 100%. Communities have some work here to be done too.
[1]: http://underhanded-c.org/