vuls FTBFS for riscv because of its dependency on golang-github-boltdb-bolt, which is outdated and incompatible with riscv. The upstream should update the dependency from golang-github-boltdb-bolt to golang-github-coreos-bbolt, which is an updated fork of bolt with riscv support. Full build log at [0].

[0] https://buildd.debian.org/status/fetch.php?pkg=vuls&arch=riscv64&ver=0.7.0-1&stamp=1581053039&raw=0

github.com/boltdb/bolt
# github.com/boltdb/bolt
src/github.com/boltdb/bolt/bolt_unix.go:62:15: undefined: maxMapSize
src/github.com/boltdb/bolt/bucket.go:135:15: undefined: brokenUnaligned
src/github.com/boltdb/bolt/db.go:101:13: undefined: maxMapSize
src/github.com/boltdb/bolt/db.go:317:12: undefined: maxMapSize
src/github.com/boltdb/bolt/db.go:335:10: undefined: maxMapSize
src/github.com/boltdb/bolt/db.go:336:8: undefined: maxMapSize
src/github.com/boltdb/bolt/freelist.go:169:19: undefined: maxAllocSize
src/github.com/boltdb/bolt/freelist.go:176:14: undefined: maxAllocSize
src/github.com/boltdb/bolt/freelist.go:204:17: undefined: maxAllocSize
src/github.com/boltdb/bolt/freelist.go:207:7: undefined: maxAllocSize
src/github.com/boltdb/bolt/freelist.go:207:7: too many errors

Dear submitter,

as the package vuls has just been removed from the Debian archive
unstable we hereby close the associated bug reports.  We are sorry
that we couldn't deal with your issue properly.

For details on the removal, please see https://bugs.debian.org/1121636

The version of this package that was in Debian prior to this removal
can still be found using https://snapshot.debian.org/.

Please note that the changes have been done on the master archive and
will not propagate to any mirrors until the next dinstall run at the
earliest.

This message was generated automatically; if you believe that there is
a problem with it please contact the archive administrators by mailing
ftpmaster@ftp-master.debian.org.

Debian distribution maintenance software
pp.
Thorsten Alteholz (the ftpmaster behind the curtain)