I got this while launching
[16:22:48] [main/FATAL]: A critical error occurred net.fabricmc.loader.discovery.ModResolutionException: Could not find required mod: canvas requires {fabric-renderer-api-v1 @ [*]} at net.fabricmc.loader.discovery.ModResolver.findCompatibleSet(ModResolver.java:198) ~[fabric-loader-0.11.6.jar:?] at net.fabricmc.loader.discovery.ModResolver.resolve(ModResolver.java:832) ~[fabric-loader-0.11.6.jar:?] at net.fabricmc.loader.FabricLoader.setup(FabricLoader.java:195) ~[fabric-loader-0.11.6.jar:?] at net.fabricmc.loader.FabricLoader.load(FabricLoader.java:185) [fabric-loader-0.11.6.jar:?] at net.fabricmc.loader.launch.knot.Knot.init(Knot.java:132) [fabric-loader-0.11.6.jar:?] at net.fabricmc.loader.launch.knot.KnotClient.main(KnotClient.java:28) [fabric-loader-0.11.6.jar:?] Caused by: net.fabricmc.loader.util.sat4j.specs.ContradictionException: Creating Empty clause ? at net.fabricmc.loader.util.sat4j.minisat.constraints.cnf.Clauses.propagationCheck(Clauses.java:117) ~[fabric-loader-sat4j-2.3.5.4.jar:?] at net.fabricmc.loader.util.sat4j.minisat.constraints.cnf.Clauses.sanityCheck(Clauses.java:97) ~[fabric-loader-sat4j-2.3.5.4.jar:?] at net.fabricmc.loader.util.sat4j.minisat.constraints.MixedDataStructureDanielWL.createClause(MixedDataStructureDanielWL.java:81) ~[fabric-loader-sat4j-2.3.5.4.jar:?] at net.fabricmc.loader.util.sat4j.minisat.core.Solver.addClause(Solver.java:401) ~[fabric-loader-sat4j-2.3.5.4.jar:?] at net.fabricmc.loader.discovery.ModResolver.findCompatibleSet(ModResolver.java:195) ~[fabric-loader-0.11.6.jar:?] ... 5 more
Actually I have a canvas-1.0.1582 in my mods folder,and fabric 0.11.6 ready
If I remove canvas from mods folder,my game can launch as usual

You need to install Fabric API in addition to Fabric loader. It's available on CurseForge.

It works! Thanks a lot!:)